Sunday, December 18, 2011
Sunday Spinelessness - A rare case of secondary spinelessness
These Sunday posts are about celebrating the spineless multitude - that under-appreciated majority of animal-life that makes it way around the world without the aid of a backbone. We usualy call thsoe creatures "invertebrates", but that name doesn't apply to an actual taxonomic group. These days, taxonomists generally classify organisms based on their shared evolutionary history. So although having a backbone might been the most obvious factor that groups the species in the sub-phylum Vertebrata together, the reason we place fishes, reptiles, amphibians birds and mammals together is the fact they as a group, they are more closely related to each other than any other animals. In fact, the presence of vertebrae in all these groups is one of the reasons we know they are related to each other - since it's much more likely that the modern species each inherited their backbones from a common ancestor than each coming up with the idea on their own. The "invertebrates" are simply all the animal species that don't fall into the group Veterbrata, by they are not a natural group because some of them (like sea-squirts) are much more closely related to vertebrates that other inverts.
Ok. So the entire post up until this point was a setup for a terrible 'joke' (and an excuse to shoehorn some "news" into the Sunday post). For those reading from outside New Zealand, a chocolate fish is a marshmallow (Athaea) filled, chocolate (cacao) covered fish (piscus) shaped confectionery, which has somehow become the standard currency for a small job well done. In that spirit, the doctoral office here at Otago gives everyone that actually makes it to the end of the small task of writing and submitting their PhD thesis a chocolate fish. This is my chocolate fish.
I'd write about my thoughts about the PhD process, the struggles of writing and the inevitable dramas of printing the thing, but I'm not sure my thoughts have caught up with me yet. I'm mainly in the "wandering around the house unsure what to do with myself stage" for now. So if you'll excuse me, I'll get back to that.
Using the evolutionary history of species as a way to classify them leads to some slightly ill-fitting names. The mammalian order Carnivora includes the Panda (an animal that very rarely eats anything other than bamboo) and snakes are still tetrapods even if that name means "four-footed". As far as I know, there is only one species of vertebrate that lacks a backbone and might therefor sneak in to these posts, the New Zealand endemic Cacaopiscus althaea "or chocolate fish":
Ok. So the entire post up until this point was a setup for a terrible 'joke' (and an excuse to shoehorn some "news" into the Sunday post). For those reading from outside New Zealand, a chocolate fish is a marshmallow (Athaea) filled, chocolate (cacao) covered fish (piscus) shaped confectionery, which has somehow become the standard currency for a small job well done. In that spirit, the doctoral office here at Otago gives everyone that actually makes it to the end of the small task of writing and submitting their PhD thesis a chocolate fish. This is my chocolate fish.
I'd write about my thoughts about the PhD process, the struggles of writing and the inevitable dramas of printing the thing, but I'm not sure my thoughts have caught up with me yet. I'm mainly in the "wandering around the house unsure what to do with myself stage" for now. So if you'll excuse me, I'll get back to that.
Labels: sci-blogs, sunday spinelessness
Sunday, December 11, 2011
(repost) Sunday Spinelessness - The origin and extinction of species
I'm still experiencing a severe spare-time deficiency down here, so, to stop myself from becoming one of those bloggers, here's something I prepared earlier.
I chose this post to recycle with good reason, I'm thrilled to say that an edited version of this will appear in print in The Open Lab 2012 - a collection of some of the best online science writing from the last year. Do check out the other entries that made it the anthology, and the other excellent posts that didn't quite fit into this years collection.
I don't use these pages to write about my own work very much, partly because it's not yet published and partly because I write about that all day as it is. The shortest answer I can provide to the question "what do you do" is "I use genetic tools to study evolution" and I guess that makes me an evolutionary geneticist. You can split the people that work in our field into two groups: there are biologists that are really interested in a group of organisms and have learned some genetics to help their study of them, and there are people who are interested in a particular question and have chosen their study organisms to suit. I'm very much of the second sort, and like most people in that group I've caught myself saying "I'm interested in the questions, not the animals". Paraphrased, that becomes something like, "Oh sure, I study Pacific land snails, but for all I care they're just little bags of genes that help me answer questions". But that's a lie. You can't work on animals without having them effect you. When I started my PhD I had no particular love of snails, but now I'm a complete snail fan-boy and I frequently find myself preaching on the wonders of life as a terrestrial mollusc to people whose only mistake was to ask me what I do for a living. Did you know most slugs retain the remnants of their shells? Or that almost all snail shells coil to the right? Or that mating in many land snail species only proceeds after one snail has stabbed the other with a "love dart"? A couple of weeks ago I was recounting the the sad tale of The Society Islands partulids to someone I'd met three minutes earlier, and today I'm going to tell you that story (though, of course you have an advantage over the first recipient of the story, since you don't have to read this crap)
Believe it or not, land snails are one of the characteristic animals of Pacific Islands. Anak krakatau is so young it's still smoldering, and it has a native land snail species and Rapa nui (Easter Island), which is arguably the most isolated island in the Pacfic, had its own land snail fauna back when it had forests. It's not entirely clear how these unlikely colonists get to islands. Darwin was so interested in the question* he, ever the experimentalist, stuck snails to ducks' feet to see if they'd survive an inter-island journey. Birds have been shown to carry snails great distances, but wind blown leaves are probably a more common mode of conveyance. We might not know exactly how snails get to islands, but we know what happens once they establish themselves. The land snails of the Pacific include some of the most outrageous explosions of diversity in the biological world. Chief among these evolutionary radiations were the partulid snails of The Society Islands (the French Polynesian archipelago that includes Tahiti). Partulids are very elegant tree snails that form part of the land snail fauna across most of Polynesia, in the Societies they made up most of the land snail fauna. In total, the tiny islands had 58 species of these snails with each of the main islands have their own endemic forms.
Those massive tables (there are more than 100 pages of them in the Moorean monograph) might seem like an old-fashioned, descriptive, way to do biology. But in many ways Crampton was ahead of his time. For one, he was a Darwinist when not every evolutionist was. By the end of the 19th century Darwin had convinced the world of the fact evolution had happened, but relatively few naturalist bought his theory of how evolutionary change happened. The anti-Darwinian theories that prospered during the so called "eclipse of Darwinism" placed very little importance on the variation within species. The orthogenesists and the lamarckians thought evolution had a driving force, pushing species towards perfection. In their scheme variation within a species was deviance from the mainstream of evolution and was quckly stamped out by natural selection (which they didn't deny, they just said it couldn't be a creative force). Similarly, saltationists thought large-scale evolutionary changes occurred in a single generation, and the small changes you see in populations were of no consequence in the grand scheme of evolution. Crampton realised that, in a Darwinian world, variation within populations was the raw material of evolution. He was obsessive about measuring his shells because he knew could use the data he was recording to understand where species came from. In particular, we was able to show that isolated populations of the same species varied from each other. That finding that makes sense in light of Darwin's theory, since species arise from populations evolving away from each other; but is harder to fit into progressive theories of evolution, in which you'd expect different populations of the same species to follow the same trajectory.
Crampton's results influenced people like Dobzhanky, Mayr and Huxley who helped to re-establish Darwinism as the principal theory of evolution in the Modern Evolutionary Synthesis. But Crampton also predicted arguably the most important development in evolutionary theory since the modern synthesis. In the middle of the 20th century evolutionary genetics was defined by a single debate. The "classical" school held that populations in the wild would have almost no genetic variation, because for every gene there would be one 'best' version and every member of the population would have two copies of that gene. Arguing against the classical school, the "balance" school argued that, quite often, there would be no single best gene and organisms would do better having two different versions of the same gene**. The ballancers thought natural selection would keep lots of different versions of maybe 10% of a species' genes. Both schools assumed natural selection was such a pervasive force that selection would dictate the way populations were made up, they just disagreed on what would result from it. Here's the funny thing, they were both spectacularly wrong. When scientists started being able to measure he genetic diversity of populations in the 1960s it became clear almost every single gene had multiple different versions. Now, in the post-genomic age there is a database with 30 million examples of one sort of genetic variant amongst humans.
Faced with the overwhelming variation he recorded in partulid shells, Crampton had argued natural selection didn't have a damn thing to do with it. Snails isolated from each other by a mountain weren't adapting to their local habitat, they just varied with respect to traits that had no influence on their survival. The fact two populations were isolated meant each would follow its own path and two populations could drift apart from each other. Faced with the overwhelming genetic variation coming from studies in the 1960s Motoo Kimura proposed the neurtral theory of molecualr evolution. Kimura's explanation was the same as Crampton's, almost all of the variation we see at genetic level has no bearing on the success or failure or organisms so the frequency of different variants drifts around at random. The neutral theory is at the heart of a lot of modern evolutionary genetics, and Crampton had understood the underlying principle 50 years before we knew we needed it!
At the end of his monograph on the partulids of Moorea, Crampton said he'd got as far as his measurements could take him, and it was time for someone to study their genetics. In took a bit longer than Crampton might have hoped, but in the 1960s two leading geneticists took up the study of his snails. James Murray from Virginia and Bryan Clarke from Nottingham spent almost 20 years working in what they called, in more than one paper, the perfect "museum and laboratory" in which to study the origin of species. Their work helped scientists understand, among other things, how ecology can contribute the formation of new species and what happens to species when they hybridise with others from time to time. Then, in 1984, Murray and Clarke had to write the most heart-breaking scientific paper I've ever read. It's written in the careful prose scientists use to talk to each other, but the message it delivered was devestating:
I should end by saying there is just a tiny scrap of good news in this story. The partulids are no longer an iconic species in the study of evolution, but they have become the pandas of invertebrate conservation. Murray and Clarke were able to get 15 of the species of the islands and into zoos and labs across the Northern Hemisphere. Breeding programs have been succesful, and new lab-based studies come out form time to time. The relict populations back in the Societies don't have nearly the range they used to, but it appears they've held on to most of their original genetic variation. Perhaps, one day, Eulglandina can be taken care of and some of the partulids can have their islands back.
*Darwin had to be interested in dispersal. Before evolution was widely accepted naturalists thought creatures were created for their habitat (the modern creationist notion of a post-flood diaspora explaining the distribution of animals is almost entirely an invention of Seventh Day Adventists, no, really, it is), Darwin's theory did away with special creation but still needed to explain how life came to live everywhere
** A concept similar to "hybrid vigour", in which crosses between relatively unrelated strains/cultivar bring together different genes and do well as a result. You've seen evidence of this phenomenon any time you've eaten yellow and white "honey and pearl" corn. That corn is a hybrid between a white and yellow cultivar and if you count up the kernals you should get close to the 3:1 ratio Mendel preficts for a dihybrid cross.
Some further reading:
Stephen Jay Gould, who was a snail man himself, wrote and essay on Crampton and the Society Island partulids in which made a humanistic argument for the importance conservation. I resisted the urge to re-read it in researching this piece so anything I stole from him I stole sub-consciously!
Crampton's monograph on the Mooeran partulids (from which the figures above are taken) is available online
I chose this post to recycle with good reason, I'm thrilled to say that an edited version of this will appear in print in The Open Lab 2012 - a collection of some of the best online science writing from the last year. Do check out the other entries that made it the anthology, and the other excellent posts that didn't quite fit into this years collection.
I don't use these pages to write about my own work very much, partly because it's not yet published and partly because I write about that all day as it is. The shortest answer I can provide to the question "what do you do" is "I use genetic tools to study evolution" and I guess that makes me an evolutionary geneticist. You can split the people that work in our field into two groups: there are biologists that are really interested in a group of organisms and have learned some genetics to help their study of them, and there are people who are interested in a particular question and have chosen their study organisms to suit. I'm very much of the second sort, and like most people in that group I've caught myself saying "I'm interested in the questions, not the animals". Paraphrased, that becomes something like, "Oh sure, I study Pacific land snails, but for all I care they're just little bags of genes that help me answer questions". But that's a lie. You can't work on animals without having them effect you. When I started my PhD I had no particular love of snails, but now I'm a complete snail fan-boy and I frequently find myself preaching on the wonders of life as a terrestrial mollusc to people whose only mistake was to ask me what I do for a living. Did you know most slugs retain the remnants of their shells? Or that almost all snail shells coil to the right? Or that mating in many land snail species only proceeds after one snail has stabbed the other with a "love dart"? A couple of weeks ago I was recounting the the sad tale of The Society Islands partulids to someone I'd met three minutes earlier, and today I'm going to tell you that story (though, of course you have an advantage over the first recipient of the story, since you don't have to read this crap)
Believe it or not, land snails are one of the characteristic animals of Pacific Islands. Anak krakatau is so young it's still smoldering, and it has a native land snail species and Rapa nui (Easter Island), which is arguably the most isolated island in the Pacfic, had its own land snail fauna back when it had forests. It's not entirely clear how these unlikely colonists get to islands. Darwin was so interested in the question* he, ever the experimentalist, stuck snails to ducks' feet to see if they'd survive an inter-island journey. Birds have been shown to carry snails great distances, but wind blown leaves are probably a more common mode of conveyance. We might not know exactly how snails get to islands, but we know what happens once they establish themselves. The land snails of the Pacific include some of the most outrageous explosions of diversity in the biological world. Chief among these evolutionary radiations were the partulid snails of The Society Islands (the French Polynesian archipelago that includes Tahiti). Partulids are very elegant tree snails that form part of the land snail fauna across most of Polynesia, in the Societies they made up most of the land snail fauna. In total, the tiny islands had 58 species of these snails with each of the main islands have their own endemic forms.
A plate from Crampton's monograph on the partulids of Moorea
The Society Islands' land snails were a marvel all by themselves, but they were also an extraordinary resource for scientists. The first person to seriously take up their study was the American embryologist and evolutionary biologist Henry Crampton. Crampton was working at the turn of the 20th century, a time in which the mechanisms underlying genetics and evolution were very much up for debate, and he hoped Tahitian and Moorean partulids could help set the story straight. Crampton's monogrpahs are famous (at least among people that spend thier lives thinking about snails) for their detail. He collected and measured over two hundred thousand shells, then calculated summary statistics for each species, each site and each measurement. By hand. To eight decimal places. Those massive tables (there are more than 100 pages of them in the Moorean monograph) might seem like an old-fashioned, descriptive, way to do biology. But in many ways Crampton was ahead of his time. For one, he was a Darwinist when not every evolutionist was. By the end of the 19th century Darwin had convinced the world of the fact evolution had happened, but relatively few naturalist bought his theory of how evolutionary change happened. The anti-Darwinian theories that prospered during the so called "eclipse of Darwinism" placed very little importance on the variation within species. The orthogenesists and the lamarckians thought evolution had a driving force, pushing species towards perfection. In their scheme variation within a species was deviance from the mainstream of evolution and was quckly stamped out by natural selection (which they didn't deny, they just said it couldn't be a creative force). Similarly, saltationists thought large-scale evolutionary changes occurred in a single generation, and the small changes you see in populations were of no consequence in the grand scheme of evolution. Crampton realised that, in a Darwinian world, variation within populations was the raw material of evolution. He was obsessive about measuring his shells because he knew could use the data he was recording to understand where species came from. In particular, we was able to show that isolated populations of the same species varied from each other. That finding that makes sense in light of Darwin's theory, since species arise from populations evolving away from each other; but is harder to fit into progressive theories of evolution, in which you'd expect different populations of the same species to follow the same trajectory.
Crampton's results influenced people like Dobzhanky, Mayr and Huxley who helped to re-establish Darwinism as the principal theory of evolution in the Modern Evolutionary Synthesis. But Crampton also predicted arguably the most important development in evolutionary theory since the modern synthesis. In the middle of the 20th century evolutionary genetics was defined by a single debate. The "classical" school held that populations in the wild would have almost no genetic variation, because for every gene there would be one 'best' version and every member of the population would have two copies of that gene. Arguing against the classical school, the "balance" school argued that, quite often, there would be no single best gene and organisms would do better having two different versions of the same gene**. The ballancers thought natural selection would keep lots of different versions of maybe 10% of a species' genes. Both schools assumed natural selection was such a pervasive force that selection would dictate the way populations were made up, they just disagreed on what would result from it. Here's the funny thing, they were both spectacularly wrong. When scientists started being able to measure he genetic diversity of populations in the 1960s it became clear almost every single gene had multiple different versions. Now, in the post-genomic age there is a database with 30 million examples of one sort of genetic variant amongst humans.
Faced with the overwhelming variation he recorded in partulid shells, Crampton had argued natural selection didn't have a damn thing to do with it. Snails isolated from each other by a mountain weren't adapting to their local habitat, they just varied with respect to traits that had no influence on their survival. The fact two populations were isolated meant each would follow its own path and two populations could drift apart from each other. Faced with the overwhelming genetic variation coming from studies in the 1960s Motoo Kimura proposed the neurtral theory of molecualr evolution. Kimura's explanation was the same as Crampton's, almost all of the variation we see at genetic level has no bearing on the success or failure or organisms so the frequency of different variants drifts around at random. The neutral theory is at the heart of a lot of modern evolutionary genetics, and Crampton had understood the underlying principle 50 years before we knew we needed it!
At the end of his monograph on the partulids of Moorea, Crampton said he'd got as far as his measurements could take him, and it was time for someone to study their genetics. In took a bit longer than Crampton might have hoped, but in the 1960s two leading geneticists took up the study of his snails. James Murray from Virginia and Bryan Clarke from Nottingham spent almost 20 years working in what they called, in more than one paper, the perfect "museum and laboratory" in which to study the origin of species. Their work helped scientists understand, among other things, how ecology can contribute the formation of new species and what happens to species when they hybridise with others from time to time. Then, in 1984, Murray and Clarke had to write the most heart-breaking scientific paper I've ever read. It's written in the careful prose scientists use to talk to each other, but the message it delivered was devestating:
In an attempt to control the numbers of the giant African snail, Achatina fulica, which is an agricultural pest, a carnivorous snail, Euglandina rosea; has been introduced into Moorea. It is spreading across the island at the rate of about 1.2 km per year, eliminating the endemic Partula. One species is aiready extinct in the wild ; and extrapolating the rate of spread of Euglandina , it is expected that all the remaining taxa (possibly excepting P. exigua) will be eliminated by 1986-1987.
The bad guys: Euglandina on the left, Achatina on the right.
Euglandina rosea is better known as the Rosy Wolf Snail. It senses the mucous trails of other snails, tracks them down and eats them. It's not clear if the wolf snail had any effect on the pest species it was introduced to control, but it had huge impact on the partulids. By the time Murray and Clarke wrote their paper, E. rosea had already done for one species and it was too well established to control. All they could do was watch as human stupidity and molluscan hunger slowly (1.2 km per year) destroyed the species they'd been studying for 20 years and Crampton had dedicated 50 years of his life to. The same slow torture played itself out in Tahiti and then the rest of the Society Islands. Where there were 58 named species, there are now 5 alive in the wild. Crampton's hundreds of pages of tables should have been the starting point from which the evolution of the partulids could have been tracked. Murray and Clarke's natural laboratory should still be open and be taking advantage of a new generation of technologies that might be able to reveal the genetic and genomic changes that occur when a new species arises. Extinction is a natural part of life, and the fate of all species eventually, but when it's driven by human short-sightedness and robs us of not just a wonderful product of nature but a window through which we might have understood nature's working it's very hard to write about.I should end by saying there is just a tiny scrap of good news in this story. The partulids are no longer an iconic species in the study of evolution, but they have become the pandas of invertebrate conservation. Murray and Clarke were able to get 15 of the species of the islands and into zoos and labs across the Northern Hemisphere. Breeding programs have been succesful, and new lab-based studies come out form time to time. The relict populations back in the Societies don't have nearly the range they used to, but it appears they've held on to most of their original genetic variation. Perhaps, one day, Eulglandina can be taken care of and some of the partulids can have their islands back.
*Darwin had to be interested in dispersal. Before evolution was widely accepted naturalists thought creatures were created for their habitat (the modern creationist notion of a post-flood diaspora explaining the distribution of animals is almost entirely an invention of Seventh Day Adventists, no, really, it is), Darwin's theory did away with special creation but still needed to explain how life came to live everywhere
** A concept similar to "hybrid vigour", in which crosses between relatively unrelated strains/cultivar bring together different genes and do well as a result. You've seen evidence of this phenomenon any time you've eaten yellow and white "honey and pearl" corn. That corn is a hybrid between a white and yellow cultivar and if you count up the kernals you should get close to the 3:1 ratio Mendel preficts for a dihybrid cross.
Some further reading:
Stephen Jay Gould, who was a snail man himself, wrote and essay on Crampton and the Society Island partulids in which made a humanistic argument for the importance conservation. I resisted the urge to re-read it in researching this piece so anything I stole from him I stole sub-consciously!
- Gould, S.J., 1994. Unenchanted evening in Eight Little Piggies: Reflections in Natural History
- Crampton, H.E., 1932. Studies on the variation, distribution, and evolution of the genusPartula. The species inhabiting Moorea. Carnegie Institution of Washington, 410, 1335.
- Clarke, B., Murray, J. & Johnson, M.S., 1984. The extinction of endemic species by a program of biological control. Pacific Science, 38(2), 97-104.
Labels: phoning-it-in, sci-blogs, sunday spinelessness
Sunday, December 4, 2011
Sunday Spinelessness - Giant weta are amazing... but not the biggest bugs
I'm probably as big a cheerleader as you'll find for New Zeland's unique and wonderful invertebrates. So, you'd think I'd be happy to see one of our insects make the pages (or the pixels) of the The Daily Mail, The Sun, Boing Boing, The Huffington Post, The Mirror, The Times of India, io9 and damn near every other blog and newspaper in the world. Instead, I've spend the whole time feeling like the grinch that stole the gloss from the headlines.
The story, as it was presented in the tabloids at least, goes that an American tourist traveled to a remote island of the coast of New Zealand where he spent several days searching for a fabled giant bug before finally uncovering the creature and in the process breaking the record for the largest ever insect.
The story, as it was presented in the tabloids at least, goes that an American tourist traveled to a remote island of the coast of New Zealand where he spent several days searching for a fabled giant bug before finally uncovering the creature and in the process breaking the record for the largest ever insect.
The only problem with the story is that every single detail of it is wrong. The "American tourist" is, in fact, Mark Moffett, former curator of Ants at the Havard Museum of Comparative Zoology turned explorer and a constant feature in National Geographic and in various other media. Little Barrier Island isn't particularly remote; it's two hours boat ride from Auckland, almost always has scientific and conservation workers living on it and even has electricity provided by a solar panels. The insect in this photograph is certainly endangered, but it's apparently not very hard to find on Little Barrier. Most importantly, there is really no way that the insect chomping down on a carrot in this photograph is the largest insect ever recorded.
The creature in question is a Giant Weta, wetapunga ("god of ugly things") in Māori and Deinacrida heteracantha ("mighty locust with differing spines") in Latin. Here in New Zealand, we give the name "weta" to a large and taxonomically diverse group of cricket-like insects. Most weta are relatively small, not much larger than what you might think of as a standard cricket. Even the small species have a way of freaking people out. Cave weta (called "camel crickets" in other countries that have them) often roost in piles of firewood - I don't know how many logs have been dropped on how many toes as a result of long antennae an spindly legs poking out form an armful of wood. Perhaps even worse, ground weta (like the hibernating one I recently disturbed) seek cool and dark roosts for the day time, so frequently sleep inside shoes, much to the alarm of those owners who blindly poke their toes into them and meet resistance.
People that are scared of the smaller weta probably don't want to contemplate the eleven species of giant weta that make up the genus Deinacrida. The body of these species is about 10 cm long, and they have antennae and legs to add to that (they don't as io9 and several other outlets suggested, have a "wingspan", what, with them being flightless). Although the reporting of Moffett's "discovery" has made a lot about this being the biggest ever giant weta, it's been rather short on actual numbers. In fact, the one number that keeps coming up in reports is 71 grams. That's the current record for the heaviest adult insect, and it belongs to a Little Barrier Island Giant Weta, but there is no way the one in this photo can come close to it. In the wild, once weta have mated they move down from the trees in which they live and deposit their eggs deep into soil via that impressive "spike" they carry on their back-end (which is called an ovipositor). However, if you keep giant weta in captivity, unmated and with no access to soil in which to deposit their eggs, they just accumulate egg after egg after egg. The 71 gram behemoth that holds the current record was a captive female, which was retaining eggs and, so, quite unlike anything that would be crawling around trees on Little Barrier. In the wild females with eggs might be able to maintain a weight close to 40 grams. According to people who know, the female pictured with the carrot here isn't particularly big for the Little Barrier species, so there is no reason to think she approaches the record holder.
I feel a little unpatriotic about this, but I also have to point out that even that 71 gram beast isn't the largest insect in the world. Goliath beetles (from the scarab beetle family) and the titan beetle (a long horn beetle) probably both beat the the local contender on this front. The internet is full of claims of adult goliath beetles weighing up to 100 grams, but this appears to be one of those fact-like-objects that are often repeated but have no basis in reality. David M. Williams, who has tried to get to the bottom of the largest insect problem, thinks it might be a result of the the reasonable metric measure "35 grams" entering an imperial brain as "3.5 oz". In fact, it seems adult goliath beetles probably weight in the order of 30-50 grams - quite likely more than the natural range for giant weta. The titan beetle is longer than the goliath, but it's not clear that these beetles are bulky enough to weigh more than the giant scarabs. What is clear however, is that the larvae of goliath beetles leave weta in the shade. These 13 cm long grubs tip the scales at around 80-100 grams. Scientists have yet to find the larvae of titan beetles, but they may well get even bigger. I struggle to see a good reason to restrict the "largest insect" to only adult forms, so I'm afraid the weta will have to lose that crown.
I really do feel awful about being such a downer on this rare occasion of a New Zealand invertebrate getting some exposure in the worlds's press. I trust the poor reporting that came out of the story can be blamed on the tabloids that broke it and the other sources which ran it without doing any checks, and that it's not a case of someone trying to buy themselves a headline by flying into the country and spotting an insect they knew they'd find. Still, it's shame that the stories have been about the bogus "discovery" of this animal, and the claim that it's a record breaker, because there are plenty of good reasons to talk about giant weta. In many ways, these bugs are a prefect example of the wierdness of biology in New Zealand. Our islands are just isolated enough from the rest of the world that, for the most part, invasions from overseas are rare and the bulk of species that live here live nowhere else. Those species that do establish themselves need to adapt to unique conditions and interactions that come with life on our islands, and the results are often very strange indeed. Where else would you end up with the kakapo, a giant flightless parrot in which the males attract mates with a near sub-sonic "boom" that is broadcast up to 5 kilometers from its origin. Giant weta might not be quite as bizarre as the kakapo, but they are a huge flightless cricket that has adapted to life entirely in the trees - that's pretty cool.
The giant weta exemplify another story that is too common in the New Zealand flora and fauna. The weta and the kakapo seem to have developed in a country that was free from large mammalian predators*, and so never needed to evolve ways to escape or fight off such threats. The introduction of mice, rats, stoats, weasels and possums to our naive ecosystems, and the massive habitat losses that came at the same time, have had a disastrous effect on our natural heritage. At least 60 species of vertebrate have become extinct since human settlement, and many more invertebrates will have past unnoticed. There are about 150 kakpo left, and only a few mainland enclaves and offshore islands play host to giant weta. Most of the other weta species are doing better than the giants, but they are still having to deal with predators for which their evolutionary history provides them no counter-measures. It's easy to look at the recent history of life in New Zealand and feel forlorn - I wish I had the chance to see a pair of Huia feeding or find a half-metre long gecko - but with the weta at least we have a chance to help. The giants need to be managed, and that means we need to make sure the Department of Conservation is funded to the extend that it can live up to its name. The main threat to the smaller weta species, at least in suburban settings, are mice and rats. Providing weta with a few roosting sites that are too slim for a mammal to squeeze into in your garden is enough to stack the odds in the insects' favour. The Department of Conservation even has plans that you can use to bulid your own weta motel. And for those that think wetas are just too creepy to help in this way - I'm sure providing them safe lodgings will keep them out of your shoes!
You should check Mike Bok's great post on the biggest insects here and David Williams chapter on the same, discussed above. I'm not going to link to all the news sources that ran with the silly version of this story, by kudos to Alan Boyle at MSNBC and The New Zealand Herald for digging a bit deeper.
*There are two endemic species of bat, one of which is adatpted to feeding on the ground but probably wouldn't take on an adult giant weta. There is also a 20 million year old fossil species of mammal that was probably more distantly related to modern placental mammals than marsupials are. We know precisely nothing about how this mammal, or its relatives made a living in New Zealand but the one that got fossilised was very small.
People that are scared of the smaller weta probably don't want to contemplate the eleven species of giant weta that make up the genus Deinacrida. The body of these species is about 10 cm long, and they have antennae and legs to add to that (they don't as io9 and several other outlets suggested, have a "wingspan", what, with them being flightless). Although the reporting of Moffett's "discovery" has made a lot about this being the biggest ever giant weta, it's been rather short on actual numbers. In fact, the one number that keeps coming up in reports is 71 grams. That's the current record for the heaviest adult insect, and it belongs to a Little Barrier Island Giant Weta, but there is no way the one in this photo can come close to it. In the wild, once weta have mated they move down from the trees in which they live and deposit their eggs deep into soil via that impressive "spike" they carry on their back-end (which is called an ovipositor). However, if you keep giant weta in captivity, unmated and with no access to soil in which to deposit their eggs, they just accumulate egg after egg after egg. The 71 gram behemoth that holds the current record was a captive female, which was retaining eggs and, so, quite unlike anything that would be crawling around trees on Little Barrier. In the wild females with eggs might be able to maintain a weight close to 40 grams. According to people who know, the female pictured with the carrot here isn't particularly big for the Little Barrier species, so there is no reason to think she approaches the record holder.
I feel a little unpatriotic about this, but I also have to point out that even that 71 gram beast isn't the largest insect in the world. Goliath beetles (from the scarab beetle family) and the titan beetle (a long horn beetle) probably both beat the the local contender on this front. The internet is full of claims of adult goliath beetles weighing up to 100 grams, but this appears to be one of those fact-like-objects that are often repeated but have no basis in reality. David M. Williams, who has tried to get to the bottom of the largest insect problem, thinks it might be a result of the the reasonable metric measure "35 grams" entering an imperial brain as "3.5 oz". In fact, it seems adult goliath beetles probably weight in the order of 30-50 grams - quite likely more than the natural range for giant weta. The titan beetle is longer than the goliath, but it's not clear that these beetles are bulky enough to weigh more than the giant scarabs. What is clear however, is that the larvae of goliath beetles leave weta in the shade. These 13 cm long grubs tip the scales at around 80-100 grams. Scientists have yet to find the larvae of titan beetles, but they may well get even bigger. I struggle to see a good reason to restrict the "largest insect" to only adult forms, so I'm afraid the weta will have to lose that crown.
I really do feel awful about being such a downer on this rare occasion of a New Zealand invertebrate getting some exposure in the worlds's press. I trust the poor reporting that came out of the story can be blamed on the tabloids that broke it and the other sources which ran it without doing any checks, and that it's not a case of someone trying to buy themselves a headline by flying into the country and spotting an insect they knew they'd find. Still, it's shame that the stories have been about the bogus "discovery" of this animal, and the claim that it's a record breaker, because there are plenty of good reasons to talk about giant weta. In many ways, these bugs are a prefect example of the wierdness of biology in New Zealand. Our islands are just isolated enough from the rest of the world that, for the most part, invasions from overseas are rare and the bulk of species that live here live nowhere else. Those species that do establish themselves need to adapt to unique conditions and interactions that come with life on our islands, and the results are often very strange indeed. Where else would you end up with the kakapo, a giant flightless parrot in which the males attract mates with a near sub-sonic "boom" that is broadcast up to 5 kilometers from its origin. Giant weta might not be quite as bizarre as the kakapo, but they are a huge flightless cricket that has adapted to life entirely in the trees - that's pretty cool.
The giant weta exemplify another story that is too common in the New Zealand flora and fauna. The weta and the kakapo seem to have developed in a country that was free from large mammalian predators*, and so never needed to evolve ways to escape or fight off such threats. The introduction of mice, rats, stoats, weasels and possums to our naive ecosystems, and the massive habitat losses that came at the same time, have had a disastrous effect on our natural heritage. At least 60 species of vertebrate have become extinct since human settlement, and many more invertebrates will have past unnoticed. There are about 150 kakpo left, and only a few mainland enclaves and offshore islands play host to giant weta. Most of the other weta species are doing better than the giants, but they are still having to deal with predators for which their evolutionary history provides them no counter-measures. It's easy to look at the recent history of life in New Zealand and feel forlorn - I wish I had the chance to see a pair of Huia feeding or find a half-metre long gecko - but with the weta at least we have a chance to help. The giants need to be managed, and that means we need to make sure the Department of Conservation is funded to the extend that it can live up to its name. The main threat to the smaller weta species, at least in suburban settings, are mice and rats. Providing weta with a few roosting sites that are too slim for a mammal to squeeze into in your garden is enough to stack the odds in the insects' favour. The Department of Conservation even has plans that you can use to bulid your own weta motel. And for those that think wetas are just too creepy to help in this way - I'm sure providing them safe lodgings will keep them out of your shoes!
You should check Mike Bok's great post on the biggest insects here and David Williams chapter on the same, discussed above. I'm not going to link to all the news sources that ran with the silly version of this story, by kudos to Alan Boyle at MSNBC and The New Zealand Herald for digging a bit deeper.
*There are two endemic species of bat, one of which is adatpted to feeding on the ground but probably wouldn't take on an adult giant weta. There is also a 20 million year old fossil species of mammal that was probably more distantly related to modern placental mammals than marsupials are. We know precisely nothing about how this mammal, or its relatives made a living in New Zealand but the one that got fossilised was very small.
Labels: conservation, sci-blogs, sunday spinelessness, weta
Tuesday, November 29, 2011
Kiwis blogging about evolution
As any regular readers here may have noticed, my plate is pretty full at the moment. All you are likely to read here for the next little while are quick photo-centric posts about bugs and maybe a few results of my recreational statistics (I know, it's an illness really) on the New Zealand election.
So, if you are looking for some meatier posts about evolutionary biology and the like, you might want to know that there are a couple of other New Zealanders out there writing on these topics.
Paul McBride is a PhD student from AUT who blogs at Still Monkeys. Paul works on understanding how the ecological setting of a group's evolution can effect the patterns and rates of change observed in that group. So far, his evolutionary blogging has mostly been about junk DNA and the ways in which we know many of the sequences in genomes serve no particular purpose.
I particularly liked finding out that Susumu Ohno had provided a theoretical argument as to why most of our genome would prove to be useless way back in the 1970s -just as the first genetic sequences were being read in labs. You can add Ohno's insight to Haldane's estimate of the human mutation rate (before we knew what a gene was made of!) and Nei's use of the theory of segregation load to show that most observed genetic changes must occur without the help of natural selection and start to see the wisdom of the elders of population genetics! (Paul also blogs about beer, which suits me, and reminds me to add a post about the science of brewing to my todo list).
Jarrod Cusens is a Masters student, also at AUT, and he blogs at of trees birds and other things. I gather Jarrod's research is at the hub of evolution and ecology - specifically looking at how to some habitats end up playing host to diverse, species-rich assemblages of organisms while others are dominated by a few species.
Jarrod's recent posts include a look at a couple of schools in New Zealand who have given up the (very good) biology curriculum in favour of biblical creationism (including one, I'm said to say, in my turangawaewae), a profile of one of the birds that make the New Zealand spring, the shinning cuckoo, with a bit more of the cuckoo's special brand of parasitism and a whole bunch of quotes.
So, be sure to add Paul and Jarrod to your favourite feed reader, and if you know of any other kiwis bogging about evolution and ecology let met know in the comments.
Paul McBride is a PhD student from AUT who blogs at Still Monkeys. Paul works on understanding how the ecological setting of a group's evolution can effect the patterns and rates of change observed in that group. So far, his evolutionary blogging has mostly been about junk DNA and the ways in which we know many of the sequences in genomes serve no particular purpose.
I particularly liked finding out that Susumu Ohno had provided a theoretical argument as to why most of our genome would prove to be useless way back in the 1970s -just as the first genetic sequences were being read in labs. You can add Ohno's insight to Haldane's estimate of the human mutation rate (before we knew what a gene was made of!) and Nei's use of the theory of segregation load to show that most observed genetic changes must occur without the help of natural selection and start to see the wisdom of the elders of population genetics! (Paul also blogs about beer, which suits me, and reminds me to add a post about the science of brewing to my todo list).
Jarrod Cusens is a Masters student, also at AUT, and he blogs at of trees birds and other things. I gather Jarrod's research is at the hub of evolution and ecology - specifically looking at how to some habitats end up playing host to diverse, species-rich assemblages of organisms while others are dominated by a few species.
Jarrod's recent posts include a look at a couple of schools in New Zealand who have given up the (very good) biology curriculum in favour of biblical creationism (including one, I'm said to say, in my turangawaewae), a profile of one of the birds that make the New Zealand spring, the shinning cuckoo, with a bit more of the cuckoo's special brand of parasitism and a whole bunch of quotes.
So, be sure to add Paul and Jarrod to your favourite feed reader, and if you know of any other kiwis bogging about evolution and ecology let met know in the comments.
Labels: blog blogging, phoning-it-in, sci-blogs
Monday, November 28, 2011
How did the pollsters go?
A couple of weeks ago I wrote a post comparing the various polling companies that work in New Zealand, trying to see if there were any systematic biases in the results each company produces. In that post, it wasn't possible to compare each company's estimates to an external standard because, without an election its impossible to know exactly what the population is thinking. On Saturday night we got to know just what the electorate was thinking, and there were a couple of surprises.
So, here's the last estimate of each polling company compared with the results from Saturday night for each of the four parties that made the 5% cut:
The solid line is the election result for each party. Dashed lines are a 95% margin of error for a poll with 1 000 respondents and the given level of support
As you can see, the polls had National too high and New Zealand First too low more or less across the board. It's hard to say any company did better than the others, Roy Morgan got New Zealand First about right and were the closest to National's final result, but they made up for that by over-estimating the Green Party and under-estimating Labour.
So, why did most of the companies get New Zealand First and National wrong? Of course, it's possible that the polling companies had it right, and that people across the nation changed their minds once they had the orange felt-tip pen in their hands. It could also have something to do with who bothered to turn up on Saturday. In the run up to the election, polling companies generally reported around 15% of the electorate were undecided but about 25% didn't vote. So, some of the people who recorded a preference in a poll didn't bother to have that preference recorded in the election. As far as I know, New Zealand polling companies don't ask any questions to determine how likely a respondent is to vote, and ignoring this information could bias their results.
It's not possible to reconstruct the motivations of those people that didn't show up on Saturday, but we can look at some data at a coarser grain. If people that express a preference for New Zealand First were more likely to vote than the electorate at large (and so, not including a 'likely voter' question in polling would lower their estimate in a poll) then you might expect electorates that really pulled for that party to have higher turnout. It's not perfect, but it's all we've got, and it doesn't really fit the story. National actually had stronger support in electorates with high turnout and there isn't much going on with New Zealand First (I estimate about a 0.8% increase in support votes per 1 000 voters, but that's not near to significantly different from no increase):
So, why did most of the companies get New Zealand First and National wrong? Of course, it's possible that the polling companies had it right, and that people across the nation changed their minds once they had the orange felt-tip pen in their hands. It could also have something to do with who bothered to turn up on Saturday. In the run up to the election, polling companies generally reported around 15% of the electorate were undecided but about 25% didn't vote. So, some of the people who recorded a preference in a poll didn't bother to have that preference recorded in the election. As far as I know, New Zealand polling companies don't ask any questions to determine how likely a respondent is to vote, and ignoring this information could bias their results.
It's not possible to reconstruct the motivations of those people that didn't show up on Saturday, but we can look at some data at a coarser grain. If people that express a preference for New Zealand First were more likely to vote than the electorate at large (and so, not including a 'likely voter' question in polling would lower their estimate in a poll) then you might expect electorates that really pulled for that party to have higher turnout. It's not perfect, but it's all we've got, and it doesn't really fit the story. National actually had stronger support in electorates with high turnout and there isn't much going on with New Zealand First (I estimate about a 0.8% increase in support votes per 1 000 voters, but that's not near to significantly different from no increase):
Percentage turnout is calculated relative to total enrollment for electorate (special votes not yet included)
By the way, that graph, with such poor turnout in the electorates that with the largest proportion of Labour voters, might be depressing viewing for Labour supporters. Indeed, I'm sure they'll want to work on "getting out the vote" in the Māori electorates and South Auckland, but that pattern doesn't explain the erosion of Labour's support in this election. Turnout was low in these electorates in 2008. Here's the support for each party plotted against change in turnout for each electorate (not including special votes):
Labels: election, pretty-data, sci-blogs
Sunday, November 27, 2011
Sunday Spinelessness - How long 'till they rise up and kill us all?
The title contains everything i have to say on this video:
Labels: cephalopods, octopus, sci-blogs, sunday spinelessness
Saturday, November 26, 2011
Will early returns accurately predict tonight's outcome?
It's election day.
I'm sure that later this evening we'll be treated to one of the staples of election night coverage, results from early returns delivered with the qualifier that they are unlikely to represent a reliable estimate of the final result.
Part of that reason for that qualifier is the obvious point that any small sample only provides an uncertain estimate what's going on in the population large. That sampling error can be compounded if there is some bias that makes the early-returning booths pull further left or right than the population at large. In New Zealand at least, you'll often here people say the small polling booths that quickly count and report their results are predominantly from rural areas and, so, favor right wing parties compared with larger, urban booths. (The meme that passes among some right-wing folks, that Labour only won the 2005 election because of South Auckland voters is an example of this narrative).
So, I thought I'd see if there was any evidence for that these stories are right. It's easy to get the data from each of the 6 000 or so polling booths used in the 2008 election and munge it together to see if there is a relationship between how red or blue a booth was and how many people voted there (which is a pretty good proxy for how quickly the results will be reported):
I'm sure that later this evening we'll be treated to one of the staples of election night coverage, results from early returns delivered with the qualifier that they are unlikely to represent a reliable estimate of the final result.
Part of that reason for that qualifier is the obvious point that any small sample only provides an uncertain estimate what's going on in the population large. That sampling error can be compounded if there is some bias that makes the early-returning booths pull further left or right than the population at large. In New Zealand at least, you'll often here people say the small polling booths that quickly count and report their results are predominantly from rural areas and, so, favor right wing parties compared with larger, urban booths. (The meme that passes among some right-wing folks, that Labour only won the 2005 election because of South Auckland voters is an example of this narrative).
So, I thought I'd see if there was any evidence for that these stories are right. It's easy to get the data from each of the 6 000 or so polling booths used in the 2008 election and munge it together to see if there is a relationship between how red or blue a booth was and how many people voted there (which is a pretty good proxy for how quickly the results will be reported):
If polling booths were unbiased samples of the electorate (they really aren't...), we'd expect all 99% of the dots in these graphs to fall between those dashed lines.
As you can see, at least in 2008, the common wisdom appears to be wrong: the larger polling booths went more toward National and less toward Labour than the rest of the country.
Tonight's early results will certainly only be an indicator of where things will end up, but things won't necessary get better for left-leaning parties as the night goes on.
UPDATE Thanks for a comment from Luis Apiolaza, who suggests a better way of getting the question. These plots show the percent favouring each major party after each polling booth's data is added in order of how many votes were recorded. As you can see, it takes a long time for Natinoal's vote to approach its final number. I wonder if this is in part be an artifact of many small booths in Maori electorates? Of course, polling booths won't necessarily report in order of how many votes were cast in them.
UPDATE Thanks for a comment from Luis Apiolaza, who suggests a better way of getting the question. These plots show the percent favouring each major party after each polling booth's data is added in order of how many votes were recorded. As you can see, it takes a long time for Natinoal's vote to approach its final number. I wonder if this is in part be an artifact of many small booths in Maori electorates? Of course, polling booths won't necessarily report in order of how many votes were cast in them.
Sunday, November 20, 2011
Sunday Spinelessness - Hover fly
One of these days I'll use these posts to say something substantive and intersting about the nature of life on earth. Today is not that day. Instead, an old photo of the most common pollinators in New Zealand gardens: Melangyna novaezelandiae, the New Zealand Hover Fly:
Labels: hover-fly, sci-blogs, sunday spinelessness, Syrphidae
Sunday, November 13, 2011
Sunday Spinelessness - The 95%
No the least bit original (1,2), but fun, and entirely featuring critters that have appeared here in the last year or so:
Fans of the spineless may want to join the Octopi wall street movement of Facebook.
Labels: photos, sci-blogs, sunday spinelessness
Wednesday, November 9, 2011
Polling bias among local pollsters?
Lew from Kiwipolitco stumbled across an interesting analysis of Australian pollsters, looking at whether the methods employed by particular polling companies might lead to biases in the numbers they produce .
As that post notes, it's impossible to tell whether any particular pollster is showing a bias with respect to the real levels of support for each party, because we only find out what the whole population is thinking when we have an election. We can, however, see if a particular polling company is pulling in a different direction than others. Since I've had about all the thesis-editing I can stand for one day, I decided to see if the data I put together for those charts from this morning could tell us anything about polling bias among New Zealand pollsters.
Obviously, the first step is decide on how to find the "average" number against which all polls should be compared. I went with a local regression which just fits a smoothed line through all the points. From there you can measure how far a single estimate is from the smoothed value at the same date*:
Even if all the companies are perfectly sampling the population, we'd expect estimates from single polls to show a good deal of scatter, just because polls are estimates of the population value and come with uncertainty. Indeed, there are dots all over the place in that graph. By collating all those differences between a point and the smoothed lines for the same date we can see if any of the companies are consistently finding higher or lower estimates of a party's support:
And the answer is... sort of. It seems TV3 tends to get National a little higher and Labour a little lower than the rest of the pollsters, and perhaps the Herald goes the other way. I think trying to gain anything more meaningful than that from these results is probably the statistical equivalent of reading tea leaves, but feel free to stare at the graph and confirm your own political biases!
*You should note, this approach introduces biases of its own and you should take these results with several grains of salt. In particular Roy Morgan polls a lot more often than the other companies, so that company's polling will contribute more towards the smoothed line than others, so it's no surprise they show only small biases.
If you are interested in trends in polling bias, I have these differences plotted over time here. As always, I have the raw data here so let me know if you want a csv file to play with.
Obviously, the first step is decide on how to find the "average" number against which all polls should be compared. I went with a local regression which just fits a smoothed line through all the points. From there you can measure how far a single estimate is from the smoothed value at the same date*:
And the answer is... sort of. It seems TV3 tends to get National a little higher and Labour a little lower than the rest of the pollsters, and perhaps the Herald goes the other way. I think trying to gain anything more meaningful than that from these results is probably the statistical equivalent of reading tea leaves, but feel free to stare at the graph and confirm your own political biases!
*You should note, this approach introduces biases of its own and you should take these results with several grains of salt. In particular Roy Morgan polls a lot more often than the other companies, so that company's polling will contribute more towards the smoothed line than others, so it's no surprise they show only small biases.
If you are interested in trends in polling bias, I have these differences plotted over time here. As always, I have the raw data here so let me know if you want a csv file to play with.
Labels: election, pretty-data, sci-blogs
Election graphics
As you may have noticed, there is an election around the corner. I'm not about to subject anyone to my political opinions, but I do have an area interest in which I could probably match the most tribal Labour or National supporter for fervent opinion. Bad graphs. Being able to clearly and succinctly display data is a really important scientific skill, and it's one that some of our newspapers have so far failed to develop. Take this chart, which appeared in the Christchurch Press and is apparently showing the break-down of a recent poll (thanks to John Kerr for pointing this out on Stats Chat)
*It should be pointed out, these thresholds are really indicative rather than absolute. The real cuts with vary depending on how many votes go to parties that don't make the 5% threshold or win an electorate seat and the size of any overhang
The polling data used here is taken from Wikipedia. Contact me if you want a csv file with the dates in an R-friendly format. The stacked bar charts were done manually in Inkscape and all the other plots were done with ggplot then tweaked in Inkscape.
I have no words. I honestly have no idea why there is a third dimension in this chart, or, really what I'm meant to take from any of it. This was so bad I had to have a go at fixing it.
The point of a political poll is to tell which party, along with its idealogical allies, is likely to win a majority of the seats in parliament. Since we are talking about proportions, and there is a real "something" that those proportions add up to, this a rare case in which a pie chart (or its bastard cousin the torus) might make an effective visualisation. Even so, people are generally better and assessing differences between lengths of objects than their area, so I went with a stacked bar chart.
Of course, even MMP isn't a perfectly proportional electoral system, and, especially with the overhang likely caused by the Māori Party winning more electorate seats that their party votes alone would entitle them to, the break-down of seats in parliament won't exactly match the break-down of the party vote. Here's what would happen if these results were mirrored on election day, and Act, Mana and the Māori Party held their electorate seats while the fine people of Ohariu-Belmont remove Peter Dunne, the Member for the anti-1080 lobby.
In this case, if Act were to lose Epsom the next list seat would go to the Green Party. Of course, you shouldn't use a single poll to say anything very meaningful about what a specific result is likely to be. Polls are estimates of what's going on in the population at large, and estimates always come with uncertainty. We can go some way to quantifying that uncertainty but giving each estimate a "margin of error". Using some slightly twisty logic you can say, "we don't know what the support for the National Party really is, but if it was 52.6 %, as our poll suggests, and we did lots of surveys, each of 1000 people, then 95% of the time we'd get a result between 49.5% and 55.7%". It's hard to include that uncertainty in a stacked bar chart, so here's each estimate from that poll, along with its margin of error (the "2nd seat" line is at 1.2%, the point at which a party with an electorate seat would probably get another on the list, the "govern alone" line is 51.6%, the proportion of party votes required to get 62 seats, a majority in a 123 seat parliament*)
If the fairfax poll was the only thing we had to go on, it might give left-leaning folks (like me) some hope that the true value of the National Party support was less than the "govern alone" threshold. Unfortunately, we have a whole series of polls conducted over the course of the year that suggest National's support is pretty close to the point estimate, and there appears to be little trend across those polls (except perhaps the Green party picking up Labour supporters):
That chart munges all the political polls taken this year together, and fits a smooth line between them. But some polls are probably better than others, it's hard to take a truly representative sample of the country, and it's likely that some of the companies running the polls do a better job. So here's the trend across each polling company:
And you can do the same thing looking at each of the smaller parties.
I'm sure there are lots of ways you could improve these charts (let me know if you think of some), but surely they are all more useful than that awful one from The Press?
*It should be pointed out, these thresholds are really indicative rather than absolute. The real cuts with vary depending on how many votes go to parties that don't make the 5% threshold or win an electorate seat and the size of any overhang
The polling data used here is taken from Wikipedia. Contact me if you want a csv file with the dates in an R-friendly format. The stacked bar charts were done manually in Inkscape and all the other plots were done with ggplot then tweaked in Inkscape.
Labels: pretty-data, sci-blogs
Sunday, November 6, 2011
Sunday Spinelessness - A darkling beetle
Life continues to be busy down here in Dunedin, so this will have to be another Sunday marked by a quick photo-heavy look into the world of the spineless.
I don't pretend to be a great photographer, but I do get a lot of pleasure from recording the small creatures I come across. One of the real joys of bug photography is the way even a rank amateur like me can find something that wasn't obvious at first glance. Take this darkling beetle (tenebrionid) I found the other day. An interesting enough beetle...
...but it wasn't until I'd seen the photos that I notice those neat compound eyes, it's as id I'd found a trilobite
in my garden!
Labels: beetle, photos, sci-blogs, sunday spinelessness
Sunday, October 30, 2011
Sunday Spinelessness - Om nom nom nom
I wasn't very happy with the caterpillar photos last week, so I had another go. Still not quite there, but I think I might end up with a nice shot of these guys before they turn into moths:
Labels: caterpillar, lepidoptera, photos, sci-blogs, sunday spinelessness
Sunday, October 23, 2011
Sunday Spinelessness - Spike
Blogging is going to be slow going around here for a little while, in fact, it may just be limited to photographs of bugs from out back garden. Here's one, the absurdly spiky caterpillar of a magpie moth (taken in the glaring sun, sorry):
I can't tell if this is the endemic species Nyctemera annulata, or its cousin from across the Tasmin sea, N. amica. The latter has established itself in New Zealand, and, since the two species are very closely related and can seemingly interbreed quite happily, it seems we may be witnessing the re-amalgamation of previously seperate evolutionary lineages. The philosophical implications of such a process, and what it means for the definition of species or the goals of conservation biology (did you know DoC shoots pied stilts that pair-off with the endemic black stilt?) will have to wait until I have enough time to say something sensible about them. For now, the caterpillars are pretty cool:
Labels: environment and ecology, lepidoptera, photos, sci-blogs, sunday spinelessness
Sunday, October 16, 2011
Sunday Spinelessness - a weta
The ground weta we uncovered in the garden this afternoon, which got sick of its photoshoot and decided to round on the photographer
Labels: orthoptera, photos, sci-blogs, sunday spinelessness, weta
Sunday, October 9, 2011
Sunday Spinelessness - The other monster
I've never taken a good photo of an ant. I've tried plenty of times, but even when I've happened across queens, whose size should give the point'n'shooter the best chance to capture a passable shot, I've failed. I haven't given up though, and that's why I was spent about 15 minutes of this morning on my hands and knees pointing my camera at the little red, and slightly larger black, ants that patrol the paving stones in front of our house. I failed again, but if you spend 15 minutes contemplating the little creatures that run our world you are pretty much guaranteed to run into something interesting. Today I saw something I've never seen before
.
.
A baby harvestman! I've written about harvestmen before, they are spider-relatives which are mainly scavengers rather than hunters and don't have poison-delivering fangs. I don't know if this one is a native or the introduced European harvestman (Phalangium opilio), but New Zealand has a surprisingly large number of native harvestmen (several hundred, and likely more awaiting description) and a suprisingly large number of those are truly weird looking. Arachnids like harvestmen and spiders have two sets of appendeges associated with their head. The chelicerae are use to grasp food and direct it towards their mouths whereas the pedipalps are strangely dual-purpose organs, used almost like an extra set of legs and also to deliver sperm during mating. Earlier this year I ran across a native Palpatores which amazingly giant chelicerae:
Today, while I was lining up the baby harvestman another misshapen harvestmen ran across the paving stones:
Today, while I was lining up the baby harvestman another misshapen harvestmen ran across the paving stones:
This one has considerably shorter legs than than the Palpatores, and when you zoom in on that mouth-gear you can see it's the pedipals and not the chelicerae which are out-sized.
It's not clear why the pedipalps are so spikey. They might help males to fight to fight off challangers and secure mates, but they probably also contribute to these creature's excellent camouflage. The three forward spacing spikes on the carapace place this guy in the genus Aligidia. I took a few more photos before I let him go about his business:
Labels: arachnophilia, harvestman, Opiliones, sci-blogs, sunday spinelessness
Saturday, October 8, 2011
The Nobel Disease
Bruce A. Beutler, Jules A. Hoffmann, Saul Perlmutter, Brian Schmidt, Adam Riess, Ralph M. Steinman and Dan Shechtman. Seven new Nobel Laureates and seven new names to include in the most exclusive club in science.
The Nobel prize comes with a trip to Stockholm, a gold medal and a share of million dollar prize. But perhaps even more than that, it provides a cachet that extends beyond the world of science and into the every day. Nobel lauretes are recognized as the best of the best: people whose intellectual achievements have changed the way we think of the world. The gravitas we attach to people who can put 'Nobel Prize winning scientist' in front of their name means their opinions are afforded special status. Indeed, listening to people who ought to know what they're talking about is a pretty good way to learn about the world. But a Nobel Prize doesn't represent a barrier to sloppy thinking. In fact, if anything there seems to be tendency for acknowledgement of expertise in one area to provide an unfounded confidence to speak out on other subjects. Some laureates have fallen for the most appalling anit-scientific rubbish. So much so, the term "Nobel Prize Syndrome" or "Nobel Disease" has been coined to describe this phenomenom. So, without wishing to take any of the gloss of this year's Nobelists, here is a list of some of those that were brought low by the Nobel Disease.
real science Nobel and the Nobel Peace Prize - the latter coming for his activism for nuclear nonproliferation.
Then there was the vitamin C business. Pauling became convinced that high doses of vitamin C would cure.. well, amost everything. The initial results of Pauling's research were promising, but it soon became clear they wouldn't hold up to more rigourous tests. It seems Pauling's belief was stronger than any evidence, and he doubled down, advoacting high does of vitamin C in popular and scientific works. Today it's almost impossible to talk to an advocate of these cures without having Pauling's name thrown add you.
Also there is something is his book about being visited by a fluorescent alien raccoon.
The Nobel prize comes with a trip to Stockholm, a gold medal and a share of million dollar prize. But perhaps even more than that, it provides a cachet that extends beyond the world of science and into the every day. Nobel lauretes are recognized as the best of the best: people whose intellectual achievements have changed the way we think of the world. The gravitas we attach to people who can put 'Nobel Prize winning scientist' in front of their name means their opinions are afforded special status. Indeed, listening to people who ought to know what they're talking about is a pretty good way to learn about the world. But a Nobel Prize doesn't represent a barrier to sloppy thinking. In fact, if anything there seems to be tendency for acknowledgement of expertise in one area to provide an unfounded confidence to speak out on other subjects. Some laureates have fallen for the most appalling anit-scientific rubbish. So much so, the term "Nobel Prize Syndrome" or "Nobel Disease" has been coined to describe this phenomenom. So, without wishing to take any of the gloss of this year's Nobelists, here is a list of some of those that were brought low by the Nobel Disease.
Linus Pauling (Chemistry and Peace, Vitamin C fanatic)
Surely the saddest case. Pauling was a supreme scientist, one of the first chemists to get serious about using the tools of physical chemistry to understand the basis of biology. His most famous contribution was pioneering methods that use what we know about the nature of chemical bonds to find the structure of biological chemicals. Evolutionary biologists like me remember him as the guy the first proposed that we could use the rate of change in chemical structures to measure evolutionary time between species. He's also the only person to have won aThen there was the vitamin C business. Pauling became convinced that high doses of vitamin C would cure.. well, amost everything. The initial results of Pauling's research were promising, but it soon became clear they wouldn't hold up to more rigourous tests. It seems Pauling's belief was stronger than any evidence, and he doubled down, advoacting high does of vitamin C in popular and scientific works. Today it's almost impossible to talk to an advocate of these cures without having Pauling's name thrown add you.
Kary Mullis (Chemistry, HIV denialist)
If Pauling is the saddest case of the Nobel Disease, Kary Mulllis might just be the oddest. Mullis is credited with inventing the Polymerase Chain Reaction (PCR) - a method used hundreds of thousands of times every day in molecular biology labs around the world to amplify small, specific regions of DNA. I can't even imagine how you'd do genetics without PCR, so his achievement is certainly worth the prize. But he is seriously strange. When people talk about Mullis' personality, they emphasise his use of LSD and his love of surfing and motorbikes. I guess that's quirky, but science takes all sorts and none of those would make him unique among Nobel Laureates. However, I'm not sure there has ever been an acceptance speech quite like his. Before Mullis embarked on his career in biochemistry he had a go at being a novelist, and his speech reflected this:And now as December threatened Christmas, Jennifer, that crazy, wonderful woman chemist, had dramatically left our house, the lab, headed to New York and her mother, for reasons that seemed to have everything to do with me but which I couldn't fathom. I was beginning to learn tragedy. It differs a great deal from pathos, which you can learn from books. Tragedy is personal. It would add strength to my character and depth someday to my writing. Just right then, I would have preferred a warm friend to cook with. Hold the tragedy lessons. December is a rotten month to be studying your love life from a distance.So, I don't think much of his writing, but he won a Nobel Prize and I'm some guy writing a blog - so it's hard for me to pick on him for that. Sadly, he's done much worse. In his autobiography he claimed the theories of Ozone depletion and climate change were the result of a conspiracy between scientists and government organisations seeking to continue their funding. Even worse, he is an HIV denialist. Mullis has never done any scientific research on HIV or AIDs, but PCR is, on rare occasions, used to diagnose HIV. You can imagine the mileage that those strange people that deny the link between HIV and AIDS get from being able to say "the inventor of the PCR test doesn't even believe it!"Mullis has gone to say anti-retrovirals don't work and agree that AIDS isn't a disease that people who lead "normal, American lifestyles" run much of a risk of developing.
Also there is something is his book about being visited by a fluorescent alien raccoon.
William Shockley (Physics, Eugenicist)
Shockley invented the transistor and thus, changed the world. Apparently, he wasn't happy with one revolution and wanted to change the word again, this time by creating a brighter future through genetics. Shockley was one of those people that think Idiocracy is a documentary, and that letting people make their own reproductive decissions will inevitably lead to a genetic meltdown for society. Almost all of the reasoning that goes into these eugenic panics is flawed, but Shockley really went a long way out on a short branch. His argument amounted to "Black Americans have a lower average IQ than whites, this is a result of genetic differences, therefore environmental interventions won't alleviate these problems". Shockely was no inhibited by an understanding of genetics at any step of the reasoning that took from his poor data to his odious proposals.
Among other things, Shockley's argued those with an IQ under 100 should be paid to be sterilised, and he provided samples to the wonderfully named "Repository for Germinal Choice" (dubbed the Nobel Prize sperm bank in the media") in the hope his sperm would make the world a better place.
Among other things, Shockley's argued those with an IQ under 100 should be paid to be sterilised, and he provided samples to the wonderfully named "Repository for Germinal Choice" (dubbed the Nobel Prize sperm bank in the media") in the hope his sperm would make the world a better place.
Brian Josephson (Physics, Parapsychologist)
Josephson won his Nobel Prize for his PhD work on superconductivity. Having been awarded the prize while he was still a Reader at Cambridge (and academic rank equivalent to Associate Professor in many other countries) he can now pretty much do what he wants with his life. And what he mainly wants to do is explore the stange and wonderful world of "quantum mysticism" including ideas like telepathy and precognition. I don't really know what else to say about Josephson, except read his webpage and find out for yourself.Luc Montagnier (Medicine, Homoeopathy supporter)
Montagnier is one of the people credited with discovering HIV which, Mullis and his crew notwhistanding, has been shown to the causative agent of AIDs. A huge discovery, and one that set the basis for working on treating or even curing that disease.
Then, in 2009, Montagnier set up his own journal, and published two papers that purported to show electromagnetic signals could be recorded in water that had once had DNA in it, but had subsequently been diluted such that none could remain. That would be a truly earth shattering result, as it would change pretty much everything we know about chemistry. That would be good news for homoeopaths, because, in order for their cures to work almost everything we know about chemistry would have to change. Indeed homeopaths jumped on Montagnier's work as evidence for their quackery.
Of course, the papers are rubbish. PZ Myers goes into the details, but my favourite warning sing is that one paper went from submission to re-submission to acceptance in three days. The most earth shattering result in chemistry: read, reviewed, commented on, edited, resubmitted and accepted in three days; in Montagnier's own journal; where he is the chief editor. Of course, none of that, or the fact the even the most sympathetic and credulous reading of Montagnier's papers actually supports homoeopathy as it is practised will stop him being cited by homoeopaths at every chance.
Niko Tinbergen (Medicine, supported "Refigerator Mother" theory)
The Dutch ethologist gets special mention as showing the most rapid onset of Nobel Disease. Tinbergen used his acceptence lecture to advocate for the "Refigirator mother" theory of schizophrenia and autism - an unfounded theory that led to thousands of mothers (never, it seems, fathers) being told their children's illness were a result of their poor parenting.
Labels: Nobel Prize, sci-blogs, science, skepticism
Sunday, October 2, 2011
Sunday Spinelessness - For aussie beetles, beer bottles are an evolutionary trap
It's Nobel season. Over the next month or so, we'll hear who has received a telegram summoning them to Stockholm and to fame and fortune (the cash part of the prize is worth about 1.5 million dollars). Of course, the Nobels are a big deal. Prizes are given to recognise people who have fundamentally changed the way we think about the world or the way science works. So it's nice that in the week before we start thinking about those huge sicentific acheievements we have the Ig Nobel prizes to remind us that most science is small, and sometimes it's even prettty funny.
The Ig Nobels were set up to honour science that "first makes people laugh, then makes them think". This year's winner were announced on Friday and prizes went to researchers who trained a tortoise to yawn on command so they they could find out if yawning was contagious among these animals (it's not), a Japanese team who developed an alarm clock that wakes you up by spraying a fine mist of wasabi across the room and a team who finally provided an answer to that age-old question - "why do discus throwers get dizzy while hammer throwers don't?" (here's that answer). But perhaps the award that's done the most to make people laugh is the one presented to Darryl Gwynne and David Rentz in recognition of their studies into male Australian beetles that would rather mate with beer bottles than their female counterparts.
Gwyne and Rentz found that they could attract males just by putting beer bottles out, in 30 minutes of observation that managed to lure two of them. Sadly for J. saundersi, this battle with the bottle can have devastating effects. Gwynne observed a beetle being attacked by ants "which were biting at the soft portions of his everted genitalia" and another dead one being eaten by ants.
I have to admit, the idea of a beetle so madly fixated on a beer bottle that it will give its life in the hope of mating with it is so ridiculous as to be funny. So I'm laughing, but is there anything in this research that fulfills the Ig Nobel's other criterion and makes us think? Well, I'm not sure you and I are so different from a beetle with a pathological sexual attraction to discarded beer bottles.
J. saundersi males had a perfectly sensible approach to finding partners that only broke down when a sudden change in the environment made last generation's strategy look stupid. Any species can fall into that trap because natural selection, the process that makes organisms fit their environment, has no foresight. All that selection can do is adapt the next generation to the last habitat. Usually that's fine, but lately habitats have been changing quickly. The rapid technological change of the last few thousand years has left humans in a few evolutionary traps of our own. The most commonly cited example is about food. Until recently, foods rich in fat and sugar were pretty hard to come by. Since these foods are important for regular running of our body, we have evolved brains that reward us when we eat them. Today, our brains no longer match our environment. In most western societies fatty and sugary meals are about 10 minutes drive away and, perhaps not surprisingly, the developed world is dealing with a epidemics of obesity and type 2 diabetes.
I think there is an even more important example of this phenomenon for people that aim to live a skeptical life - our brains developed in a world quite different than the one we live in. The share volume of cognitive biases that psychologists have identified reveal how our intuitions can stray from reality. Not all of those biases arise from a mismatch between our brain and our environment. Brains aren't truth finding machines, because knowing something is true doesn't, in and of itself, provide any survival advantage. But some of these mistaken intuitions really do seem to arise from our evolutionary history. Most of the people that have ever lived have done so in bands of about 50 people. Every piece of news they ever learned about the world came through those people, and maybe a few interactions with other groups. Today, I can open a new browser tab and read one of 50 million twitter streams; or watch, read and hear news from almost anywhere on the planet. But I have still have my brain, which mainly evolved to deal with news from about 50 people, so part of me is amazed when I hear someone won the lottery three times, or someone else has given birth to three children in three different years but each at 7:43. Of course, in a world of 6.7 billion people these things have to happen, but, as much as I know that, it's hard to convince my brain these aren't amazing events.
I said this fact problem matters for skeptical types, and, indeed, our faulty intuitions can have effects at least as bad as those faced by the amorous beetles that precipitated this post. If you live in a world with 50 contacts, and one of them tells you they got sick after eating a specific sort of food, that's pretty good evidence that you should avoid that food. If you live in a world with billions of potential contacts, and one of them tells you that someone, somewhere got sick after receiving a vaccination or got better after taking a homeopathic remedy that's not evidence for anything. Just like the triple lotto winners, in a world where millions of doses of vaccine given out, someone will get sick after a vaccine whether it causes an illness or not. Thankfully, we've developed methods that help us, as much as possible, to remove our intuitions from the way we handle evidence. Together, we call those methods science and it's crucial that those methods are the heart of the way our societies develop if we are going to avoid our own evolutionary traps
So, by all means laugh at J. saundersiand his futile, fatal attempts to impregnate a glass bottle, but do try an be aware that similar traps are lurking in our own brains.
*For people outside Australiasia, a stubby is a short brown 330 mL bottle which usually contains the caramel fizz that gets called "ale" or "draught" beer down here, but is, in fact, a lager.
Thanks to Ted, the blogo-sphere's foremost beetle taxonomist for pointing out this species is not called J. saundersi, as it has been shown to be distinct from J. bakewilli the name this population bore when the paper was written
The beetles in question are Julodimorpha saundersi, a member of the jewel beetles (Buprestidae) and native to desert habitats in Australia:
Mating season has probably just finished for these beetles. Adults emerge around August and for next couple of months male J. saundersifly about the place looking for females, which are larger than the males and flightless. So, for millions of years male J. saundersihave spend their springtime looking down hoping to find large (because large females produce more eggs) shiny, amber coloured surfaces covered in dimples like those on the beetles back. And for millions of years I'm sure that worked fine. Then someone invented beer bottles, and because some people suck, beer bottles starting turning up on roadsides in the Australian desert. Apparently, some Australian stubbies* have a series of dimples across the bottom. When a J. saundersimale sees one of these bottles he presumes he's won the reproductive jackpot and found the biggest, most amber, most dimpled female to ever live and... well.. you can see what happens next for yourself:
 |
| Image © Darryl Gwynne |
I have to admit, the idea of a beetle so madly fixated on a beer bottle that it will give its life in the hope of mating with it is so ridiculous as to be funny. So I'm laughing, but is there anything in this research that fulfills the Ig Nobel's other criterion and makes us think? Well, I'm not sure you and I are so different from a beetle with a pathological sexual attraction to discarded beer bottles.
J. saundersi males had a perfectly sensible approach to finding partners that only broke down when a sudden change in the environment made last generation's strategy look stupid. Any species can fall into that trap because natural selection, the process that makes organisms fit their environment, has no foresight. All that selection can do is adapt the next generation to the last habitat. Usually that's fine, but lately habitats have been changing quickly. The rapid technological change of the last few thousand years has left humans in a few evolutionary traps of our own. The most commonly cited example is about food. Until recently, foods rich in fat and sugar were pretty hard to come by. Since these foods are important for regular running of our body, we have evolved brains that reward us when we eat them. Today, our brains no longer match our environment. In most western societies fatty and sugary meals are about 10 minutes drive away and, perhaps not surprisingly, the developed world is dealing with a epidemics of obesity and type 2 diabetes.
I think there is an even more important example of this phenomenon for people that aim to live a skeptical life - our brains developed in a world quite different than the one we live in. The share volume of cognitive biases that psychologists have identified reveal how our intuitions can stray from reality. Not all of those biases arise from a mismatch between our brain and our environment. Brains aren't truth finding machines, because knowing something is true doesn't, in and of itself, provide any survival advantage. But some of these mistaken intuitions really do seem to arise from our evolutionary history. Most of the people that have ever lived have done so in bands of about 50 people. Every piece of news they ever learned about the world came through those people, and maybe a few interactions with other groups. Today, I can open a new browser tab and read one of 50 million twitter streams; or watch, read and hear news from almost anywhere on the planet. But I have still have my brain, which mainly evolved to deal with news from about 50 people, so part of me is amazed when I hear someone won the lottery three times, or someone else has given birth to three children in three different years but each at 7:43. Of course, in a world of 6.7 billion people these things have to happen, but, as much as I know that, it's hard to convince my brain these aren't amazing events.
I said this fact problem matters for skeptical types, and, indeed, our faulty intuitions can have effects at least as bad as those faced by the amorous beetles that precipitated this post. If you live in a world with 50 contacts, and one of them tells you they got sick after eating a specific sort of food, that's pretty good evidence that you should avoid that food. If you live in a world with billions of potential contacts, and one of them tells you that someone, somewhere got sick after receiving a vaccination or got better after taking a homeopathic remedy that's not evidence for anything. Just like the triple lotto winners, in a world where millions of doses of vaccine given out, someone will get sick after a vaccine whether it causes an illness or not. Thankfully, we've developed methods that help us, as much as possible, to remove our intuitions from the way we handle evidence. Together, we call those methods science and it's crucial that those methods are the heart of the way our societies develop if we are going to avoid our own evolutionary traps
So, by all means laugh at J. saundersiand his futile, fatal attempts to impregnate a glass bottle, but do try an be aware that similar traps are lurking in our own brains.
Gwynne, D. & Rentz, D. 1983 Beetles on the bottle: male buprestids mistake stubbies for females (Coleoptera). Australian Journal of Entomology, 22, p.79-80. doi: 10.1111/j.1440-6055.1983.tb01846.x
Thanks to Ted, the blogo-sphere's foremost beetle taxonomist for pointing out this species is not called J. saundersi, as it has been shown to be distinct from J. bakewilli the name this population bore when the paper was written
Labels: beetle, sci-blogs, science, skepticism, sunday spinelessness
Sunday, September 25, 2011
Sunday Spinelessness - How chitons are tougher than stone
No time to say anything meaningful today, so here's a pretty picture of a green chiton (Chiton glaucus)
Of course, I wouldn't be a self-respecting invertebrate evangelist if I didn't try an convince you that chitons represent more than a pretty shell and a stern test for junior rock-pool hunters' ability to prize creatures from rocks. Apart from all that armour, the most interesting think about chitons is their teeth. Like most molluscs they feed with a rasp like organ called the radula, unlike most other molluscs their radulae are coated in an iron-containing mineral called magnetite. As the name suggests, magnetite is a mineral that can become magnetised (in fact, of all naturally occurring minerals its the most magnetisable) but that's not why chitons make cover their teeth in it. In order to eat, chitons need incredibly abrasive teeth that can scour away at rocks and expose algae, and that means the teeth need to be coated in a tough material.
"Normal", geologically produced magnetite is pretty tough, but, remarkably, the magnetitie that chitons produce to coat their teeth is much tougher despite being made from the same molecules. The chiton's biochemical toolkit is able to produce magnetite in which the three dimensional structure is tweaked towards a tougher end result. Professor Kate McGrath from the MacDiarmid Institute spoke about this 'biomineralisation' process as part of her contribution to the Royal Society's Marie Curie Lecture Series. Her research doesn't aim to mimic the specific ways in which organisms create chemicals, so much as learn the various tricks that evolution has discovered and see how they might be applied to either tweak or completely chain the way we make useful minerals on industrial scales.
"Normal", geologically produced magnetite is pretty tough, but, remarkably, the magnetitie that chitons produce to coat their teeth is much tougher despite being made from the same molecules. The chiton's biochemical toolkit is able to produce magnetite in which the three dimensional structure is tweaked towards a tougher end result. Professor Kate McGrath from the MacDiarmid Institute spoke about this 'biomineralisation' process as part of her contribution to the Royal Society's Marie Curie Lecture Series. Her research doesn't aim to mimic the specific ways in which organisms create chemicals, so much as learn the various tricks that evolution has discovered and see how they might be applied to either tweak or completely chain the way we make useful minerals on industrial scales.
Labels: chemistry, chitons, molluscs, photos, sci-blogs, science, sunday spinelessness
Sunday, September 18, 2011
Sunday Spinelessness - Speciation by magic
For someone that writes about evolution, I don't spend much of my time talking about the 'debate' that surrounds that topic. That's probably an artifact of living in a county that doesn't allow people who are so confused about the world that they think the bible is a biology textbook to acquire any political power. But it's also because debating whether evolution happened, a fact that no serious biologists has debated since Darwin's generation and is further confirmed with each new DNA sequence, is so utterly and spectacularly boring when you compare it with some of the real debates with evolutionary biology. So here's a little something on one debate, and the land snail shells that help swing it a little towards one side.
Some of the most contentious debates within evolutionary biology are to do with how new species arise (a process we call speciation). For instance, it's not clear how much ecology* matters when it comes to speciation. Some authors argue that speciation and ecological adaptation are usually seperate processes - the second making species distinct only after speciation has separated them. Others argue that ecological adaptation can itself be an important part of the speciation process and maybe even be enough to drive species apart.
Like many ideas in evolution, this debate goes back to Darwin's time. People who really ought to know better will sometimes tell you that, despite its name, The Origin of Species doesn't have a theory of speciation. You should tell those people to read Chapter 4. Darwin did have a theory of speciation, and it explicitly placed ecological competition between newly formed species as the key to driving species apart from each other. We've learned a few things about biology since Darwin's time, and it turns out his verbal arguments don't hold up to mathematically rigorous models of the ones genes work in populations. Natural selection can't push a population apart more quickly than genetic recombination (the mixing of genes that happens in each generation) pulls it back together. So, species can't arise soley from selection. In fact, the modern conception of speciation revolves around the flow of genes between populations. If a population isn't sharing genes with others it's free to evolve independantly and take on the properties that make species distinct.
Although people have talking about gene flow with regard to speciation since Darwin's time, Ernst Mayr is probably the person most associated with establishing this idea among evolutionary biologists. Mayr took the importance of 'reproductive isolation' to its logical extremes - arguing lack of gene flow was not just a pattern that created species but actually the definition of a species (I disagree) and that speciation almost exclusively occured because of geographical barriers that keep populations apart from each other (leaving no room for selection).
But the gene-flow conception of speciation still leaves a tiny bit of room for selection as a driver of speciation. For instance, imagine a trait that could, at once, be subject to ecological competition and prevent gene flow between members that don't share the trait. Then selection would be acting to keep diverging species away form each other at the same time as adapting them to their habitat. Sergey Gavrilets, a theoretical evolutioanry biologist, called models of speciation that rely on these sort of quirks "magic trait" models, partly to represent some scepticsm that such traits could exist in the wild. But empiricists have known for a long time that these sorts of traits really are out there. For instance, many plant eating insects only mate on their host-plant. So, if two diverging species are adapting to particular hosts plants, that same adaptation process will be preventing them from mating with each other. Other examples of these magic traits include body size in fish, beak size in birds, wing colouration in butterflies and, now, shell characters in land snails.
Snails can be left- or right-handed. Or, at least, the sprial of a snail's shell can turn clockwise (making a right-handed or dextral spiral) or anti-clockwise (a left-handed or sinistral spiral) and the direction of spiraling is decided by a single gene (inherited from the mother, suggesting in may be an imprinted gene as snail's don't have sex chromosomes) . Most species are predominately right-handed and very few individuals within a species don't match the predominant spiraling direction (I only know of one exception to this rule). In fact, I've spent more time than most people looking at snails, and I've never seen a left-handed one (trust me, I check!). There's a very good reason one individuals within one species are predominately of one spiraling direction - left-handed land snails have great trouble mating with right-handed ones. Land snails are all hermaphrodites and they mate by lining up extending their gentals through a pore on the 'spiral side' of their body (if you aren't invert-phobic, there are plenty of photographs of this process here). But mirror-image snails, espacially those with relatively flat shells, struggle to line up in this way, and when they do their shells bump into each other. For this reason, 'mirror' snails (which do arise in populations all the time) struggle to reproduce and leave few descendants.
The direction in which a snail's shell coils also has ecological implications. Animals that specialise in eating snails have adapted to attacking right-handed shells. So, for instance, Pareas snakes always attack from the left and have lopsided jaws that help them work the snail out of the shell:
From this data they concluded that sinistral Satsuma species have evolved multiple times and almost always in regions that are currently home to snail-eating snakes. So shell shape really does seem like a magic trait here - left handed shells get an ecological advantage that allows them to survive and it also prevents them from sharing genes with right handed snails.
So Satsuma snails are another example of magic traits in the wild. But I think they are an opportunity to understand a bit more about speciation. The hardest thing about studying speciation is separating the differences that cause speciation with those that arise once species stop sharing genes. In the case of Satsuma we know a change one gene caused speciation so any other traits that differentiate left- and right-handed snails living along side each other happened after the fact. The number of left-right species pairs, and the different ages of the lineages they represent gives us a unique chance to understand the how interactions between newly formed species shape their futures.
Surely that's infinitely more interesting that another round of the evolution-creation controversy?
You should also check odd Ed Yong's take on this study, which is predictably excellent.
*I'm sorry to do this, because I don't want to be one of tiresome people who complain about the way language changes, but the science of ecology is something quite different from what's fast becoming the modern definition of the word. Ecology is the study of the way organisms interact with each other and their environment and (as far as I can tell) mainly involves counting a lot of things then doing some clever statistics on the resulting numbers. It's not (directly) about conservation or sustainability and it's certainly not an idea invented by advertisers who worked out adding 'eco-' to a products name and putting it in a plain box allowed them to sell it at twice the price.
Some of the most contentious debates within evolutionary biology are to do with how new species arise (a process we call speciation). For instance, it's not clear how much ecology* matters when it comes to speciation. Some authors argue that speciation and ecological adaptation are usually seperate processes - the second making species distinct only after speciation has separated them. Others argue that ecological adaptation can itself be an important part of the speciation process and maybe even be enough to drive species apart.
Like many ideas in evolution, this debate goes back to Darwin's time. People who really ought to know better will sometimes tell you that, despite its name, The Origin of Species doesn't have a theory of speciation. You should tell those people to read Chapter 4. Darwin did have a theory of speciation, and it explicitly placed ecological competition between newly formed species as the key to driving species apart from each other. We've learned a few things about biology since Darwin's time, and it turns out his verbal arguments don't hold up to mathematically rigorous models of the ones genes work in populations. Natural selection can't push a population apart more quickly than genetic recombination (the mixing of genes that happens in each generation) pulls it back together. So, species can't arise soley from selection. In fact, the modern conception of speciation revolves around the flow of genes between populations. If a population isn't sharing genes with others it's free to evolve independantly and take on the properties that make species distinct.
Although people have talking about gene flow with regard to speciation since Darwin's time, Ernst Mayr is probably the person most associated with establishing this idea among evolutionary biologists. Mayr took the importance of 'reproductive isolation' to its logical extremes - arguing lack of gene flow was not just a pattern that created species but actually the definition of a species (I disagree) and that speciation almost exclusively occured because of geographical barriers that keep populations apart from each other (leaving no room for selection).
But the gene-flow conception of speciation still leaves a tiny bit of room for selection as a driver of speciation. For instance, imagine a trait that could, at once, be subject to ecological competition and prevent gene flow between members that don't share the trait. Then selection would be acting to keep diverging species away form each other at the same time as adapting them to their habitat. Sergey Gavrilets, a theoretical evolutioanry biologist, called models of speciation that rely on these sort of quirks "magic trait" models, partly to represent some scepticsm that such traits could exist in the wild. But empiricists have known for a long time that these sorts of traits really are out there. For instance, many plant eating insects only mate on their host-plant. So, if two diverging species are adapting to particular hosts plants, that same adaptation process will be preventing them from mating with each other. Other examples of these magic traits include body size in fish, beak size in birds, wing colouration in butterflies and, now, shell characters in land snails.
Snails can be left- or right-handed. Or, at least, the sprial of a snail's shell can turn clockwise (making a right-handed or dextral spiral) or anti-clockwise (a left-handed or sinistral spiral) and the direction of spiraling is decided by a single gene (inherited from the mother, suggesting in may be an imprinted gene as snail's don't have sex chromosomes) . Most species are predominately right-handed and very few individuals within a species don't match the predominant spiraling direction (I only know of one exception to this rule). In fact, I've spent more time than most people looking at snails, and I've never seen a left-handed one (trust me, I check!). There's a very good reason one individuals within one species are predominately of one spiraling direction - left-handed land snails have great trouble mating with right-handed ones. Land snails are all hermaphrodites and they mate by lining up extending their gentals through a pore on the 'spiral side' of their body (if you aren't invert-phobic, there are plenty of photographs of this process here). But mirror-image snails, espacially those with relatively flat shells, struggle to line up in this way, and when they do their shells bump into each other. For this reason, 'mirror' snails (which do arise in populations all the time) struggle to reproduce and leave few descendants.
The direction in which a snail's shell coils also has ecological implications. Animals that specialise in eating snails have adapted to attacking right-handed shells. So, for instance, Pareas snakes always attack from the left and have lopsided jaws that help them work the snail out of the shell:
As you might imagine, these adaptations mean the snakes are less able to attack left-handed snails. If death by snake is a big risk in a snail population, then left-handed snails, while still having a hard time when it comes to mating, will be at a distinct ecological advantage. So the direction of snail's coil could be subject to ecological selection, and it definitely presents a potential barrier to gene flow. But to be a magic trait it needs to be doing both of these things at the same time.
The Japanese land snail genus Satsuma provides a natural experiment to test this idea. Satsuma snails come in left- and right-handed forms and some populations share their homes with the snake eating Pareas iwasakii snakes. Masaki Hoso and his colleagues (Hoso et al 2010, http://dx.doi.org/10.1038/ncomms1133) looked at the distribution of left- and right-handed Satsuma species and their relationships with each other.
The Japanese land snail genus Satsuma provides a natural experiment to test this idea. Satsuma snails come in left- and right-handed forms and some populations share their homes with the snake eating Pareas iwasakii snakes. Masaki Hoso and his colleagues (Hoso et al 2010, http://dx.doi.org/10.1038/ncomms1133) looked at the distribution of left- and right-handed Satsuma species and their relationships with each other.
From this data they concluded that sinistral Satsuma species have evolved multiple times and almost always in regions that are currently home to snail-eating snakes. So shell shape really does seem like a magic trait here - left handed shells get an ecological advantage that allows them to survive and it also prevents them from sharing genes with right handed snails.
So Satsuma snails are another example of magic traits in the wild. But I think they are an opportunity to understand a bit more about speciation. The hardest thing about studying speciation is separating the differences that cause speciation with those that arise once species stop sharing genes. In the case of Satsuma we know a change one gene caused speciation so any other traits that differentiate left- and right-handed snails living along side each other happened after the fact. The number of left-right species pairs, and the different ages of the lineages they represent gives us a unique chance to understand the how interactions between newly formed species shape their futures.
Surely that's infinitely more interesting that another round of the evolution-creation controversy?
You should also check odd Ed Yong's take on this study, which is predictably excellent.
*I'm sorry to do this, because I don't want to be one of tiresome people who complain about the way language changes, but the science of ecology is something quite different from what's fast becoming the modern definition of the word. Ecology is the study of the way organisms interact with each other and their environment and (as far as I can tell) mainly involves counting a lot of things then doing some clever statistics on the resulting numbers. It's not (directly) about conservation or sustainability and it's certainly not an idea invented by advertisers who worked out adding 'eco-' to a products name and putting it in a plain box allowed them to sell it at twice the price.
Labels: environment and ecology, sci-blogs, science, snails, speciation, sunday spinelessness
All content not otherwise marked is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
