Sunday, February 3, 2013
Sunday Spinelessness - Cannibalism in the garden
The most common jumping spider in our garden, Trite auricoma, with the remains of it most recent meal... a smaller T. auricoma:
Cannibalism, animals eating members of their own species, is a pretty common and widespread behavior. Species in almost every phylum have been shown to occasionally (or frequently) eat members of their own species. Even herbivores like monarch butterfly caterpillars will eat any monarch eggs they encounter.
In spiders, the most well-studied form of cannibalism relates to mating. In a very few species male spiders will offer themselves as a meal to their mate. In so doing, males make sure their offspring get the best start in life, by providing their mother with a nutrition meal. They are often also posthumously rewarded by female, who reject other suitors and ensure the sacrificial male's legacy. The best example of this behaviour comes from the Australian red back spider (Latrodectus hasseltii). In this species males actually pirouette their way into their mate's fangs, and females take up the offer about 65% of the time. New Zealand's endemic red back relative, the katipo, does not exhibit this behavior (nor does the North American black widow, despite the name).
Such sexual cannibalism isn't known from jumping spiders (although females will certainly eat unwary males), and a wider (and earlier) shot lets you see that this was a case of a mature spider taking a younger one (males and females are about equally sized in T. auricoma).
Cannibalism, animals eating members of their own species, is a pretty common and widespread behavior. Species in almost every phylum have been shown to occasionally (or frequently) eat members of their own species. Even herbivores like monarch butterfly caterpillars will eat any monarch eggs they encounter.
In spiders, the most well-studied form of cannibalism relates to mating. In a very few species male spiders will offer themselves as a meal to their mate. In so doing, males make sure their offspring get the best start in life, by providing their mother with a nutrition meal. They are often also posthumously rewarded by female, who reject other suitors and ensure the sacrificial male's legacy. The best example of this behaviour comes from the Australian red back spider (Latrodectus hasseltii). In this species males actually pirouette their way into their mate's fangs, and females take up the offer about 65% of the time. New Zealand's endemic red back relative, the katipo, does not exhibit this behavior (nor does the North American black widow, despite the name).
Such sexual cannibalism isn't known from jumping spiders (although females will certainly eat unwary males), and a wider (and earlier) shot lets you see that this was a case of a mature spider taking a younger one (males and females are about equally sized in T. auricoma).
Labels: arachnophilia, environment and ecology, jumping spiders, photos, sci-blogs, sunday spinelessness
Sunday, January 27, 2013
Sunday Spinelessness - Native bees again
Last year, at about this time, I wrote a little about our native bees. Though I'm glad to have done my little bit to promote the existence of these all too anonymous members of our natural heritage I've always felt a little embarrassed by the photos in that post. As I admitted at the time the photos are staged. Photographing our twitchy little bees is hard - apart from being small, they zip about from flower to flower much more quickly than I can line up, let alone focus, shots.
So, to illustrate the original post I used half-drowned bees, scooped out from a swimming pool. The time it took the bees to dry out gave me a chance to take the photos, but I set them up on exactly the type of flower they'd never visit in the wild. So, not only did I cheat, but the photos I took actively misled about the true nature of bees!
So, here are some much worse photographs of native bees that do a much better job of representing their lifestyles. First off, a bee perched on a favourite flower, a hebe, and deciding on its next move:
So, to illustrate the original post I used half-drowned bees, scooped out from a swimming pool. The time it took the bees to dry out gave me a chance to take the photos, but I set them up on exactly the type of flower they'd never visit in the wild. So, not only did I cheat, but the photos I took actively misled about the true nature of bees!
So, here are some much worse photographs of native bees that do a much better job of representing their lifestyles. First off, a bee perched on a favourite flower, a hebe, and deciding on its next move:
and another collecting pollen from the same plant:
These hebes, and a few parsley plants left to go to flower, make my parent's house in the Wairarapa a mecca for native bees. They certainly make their mark around the garden, if you don't notice them drowned in the pool or visiting flowers you can see their nests in the soil:
Labels: bees, environment and ecology, native bees, photos, sci-blogs, sunday spinelessness
Sunday, January 13, 2013
Sunday Spineless - On the Wing
Just a photo today, but a pretty awesome one I reckon. An inbound bumble bee from my parents' garden in the Wairarapa:
(~50 out of focus shots from same session not shown!)
Labels: bee, bumblebee, environment and ecology, photos, sci-blogs, sunday spinelessness
Sunday, December 9, 2012
Sunday Spinelessness - A Clearwing moth
At last, Dunedin has managed to arrange a proper summer day for a weekend.
The extra heat and sun saw plenty of bugs out and about, and I spotted plenty of familiar critters (native bees, cicadas, drone flies and magpie moths) for this first time this year. The real find of the weekend though, was something entirely new to me:
You might be a little surprised to learn that you are looking at a moth.
I'm helping design an undergraduate lab on systematics and taxonomy at the moment. Since the new lab is about insects I've suddenly become very aware of the traits that distinguish various insect groups. Moths, along with butterflies, make up the order Lepidoptera. You can see a few lepitoperan characters in the above photo: a mouth designed for siphoning nectar from flowers and a body covered in fine scales.
"Lepitoptera" actually mans "scaley wing", and, indeed most butterflies and moths have scales on their wings. This species, though, has got rid of most of it's wing scales (there are plenty of scales on the trialing edge though):
I'm helping design an undergraduate lab on systematics and taxonomy at the moment. Since the new lab is about insects I've suddenly become very aware of the traits that distinguish various insect groups. Moths, along with butterflies, make up the order Lepidoptera. You can see a few lepitoperan characters in the above photo: a mouth designed for siphoning nectar from flowers and a body covered in fine scales.
"Lepitoptera" actually mans "scaley wing", and, indeed most butterflies and moths have scales on their wings. This species, though, has got rid of most of it's wing scales (there are plenty of scales on the trialing edge though):
Synanthedon tipuliformis * is member of the "clear wing" moth family Sesiidae. Although I think this one is pretty neat, the family contains some striking species, the most interesting of which are wasp-mimics
Labels: environment and ecology, lepidoptera, moths, photo, sci-blogs, sesiidae, sunday spinelessness, Synanthedon tipuliformis
Sunday, December 2, 2012
Sunday Spinelessness - Bark Lice
I should have known that the little challenge I put up last week wouldn't so much as wrinkle the brow of the bug-blogo-sphere's best. The Atavism's two homes means there were two winners. Ted MacRae of Beetles in the Bush chimed in at he blogspot version, correctly identifying the insect as a "bark louse" or psocopteran, and recognizing those stubby white protrusion as yet-to-be expanded wings . Morgan Jackson of Biodiversity in Focus did the same at SciBlogs.
*This is not a botany blog... I really have no idea what the tree is
Thanks too to Deborah from Bee of a Certain Age, who hazarded a guess that those white protrusions might be eggs. Certainly a more reasonable guess that my own first thoughts at seeing these bugs crawling over the the Big Tree* in our garden. The plump abdomens and long antennae made me think of the large (but certainly not GIANT) springtails. Ripping up a couple of pieces of bark revealed a whole colony of these odd-looking bugs, and evidence for just how wrong I was.
The adults have wings, which they hold tent-like over their bodies. Insects are the only invertebrates with wings, so, since spring tails aren't insects, my first guess was horribly inaccurate (glossing over about 400 million years of evolutionary divergence).
As Ted and Morgan worked out, these are "bark lice", members of the order Psocoptera. Although they are related to the "true lice" (Order Phthiraptera), psocopterans are not parasites. Rather, they wander around their trees eating algae, fungi and whatever detritus might be clinging to the bark. The only species that could be considered pests are the "book lice" - small flightless psocopterans that sometimes turn up in old books where they eat the paste that binds pages together. (I have it on good authority that book lice can also destroy botanical collections, so certainly a pest)
A couple of weeks ago I gave Veronika Meduna a tour of our garden and its bugs, and I gather you can hear the result on Radio New Zealand's Our Changing World next week. While I was catching my breath between talking about the mating habits of spiders, and how our native slugs are much more sluggish then their introduced counterparts she asked the obvious question - "why?". Why do I care so much about odd little creatures like bark lice and slugs and spiders? I'm not sure I managed a coherent answer at the time, but I can tell you now, spineless creatures need evangelists because most people have a very skewed view about the way biology works. If your vision of biodiversity is limited to pandas and dolphins and lions and tigers then you are missing out on millions of other ways to be alive.
Take bark lice as an example. I'll admit that I'd never given these creatures a moments thought before running into them last week. But, in researching this post I found out there are more than four thousand psocopteran species. That is to say, there are almost as many bark lice species as there are mammals - all the lions, tigers, bears, dolphins, whales, marsupials, rodents and bats in the world add up to about 5 400. That matters because species are the fundamental units of biological diversity. Each species represents a distinct evolutionary lineage - free to take up different ecological niches, develop new morphological features or occupy a different geographic range.
To try an illustrate how diverse these unassuming little critters really are, I've put together a "treemap". In the plot below, each of the stained-glass window panels represents the number of species in one psocopteran genus, nested within a family (the heavier lines, with labels ending in -DAE) which in turn is nested within a suborder (the very heaviest lines, labeled -MORPHA). These higher taxonomic ranks are not fundamental units in the way species are. Even so, species placed within a taxonomic group share evolutionary history, and are united by particular morphological characters which they share. It turns out there are quite a few ways to be a bark louse:
As Ted and Morgan worked out, these are "bark lice", members of the order Psocoptera. Although they are related to the "true lice" (Order Phthiraptera), psocopterans are not parasites. Rather, they wander around their trees eating algae, fungi and whatever detritus might be clinging to the bark. The only species that could be considered pests are the "book lice" - small flightless psocopterans that sometimes turn up in old books where they eat the paste that binds pages together. (I have it on good authority that book lice can also destroy botanical collections, so certainly a pest)
A couple of weeks ago I gave Veronika Meduna a tour of our garden and its bugs, and I gather you can hear the result on Radio New Zealand's Our Changing World next week. While I was catching my breath between talking about the mating habits of spiders, and how our native slugs are much more sluggish then their introduced counterparts she asked the obvious question - "why?". Why do I care so much about odd little creatures like bark lice and slugs and spiders? I'm not sure I managed a coherent answer at the time, but I can tell you now, spineless creatures need evangelists because most people have a very skewed view about the way biology works. If your vision of biodiversity is limited to pandas and dolphins and lions and tigers then you are missing out on millions of other ways to be alive.
Take bark lice as an example. I'll admit that I'd never given these creatures a moments thought before running into them last week. But, in researching this post I found out there are more than four thousand psocopteran species. That is to say, there are almost as many bark lice species as there are mammals - all the lions, tigers, bears, dolphins, whales, marsupials, rodents and bats in the world add up to about 5 400. That matters because species are the fundamental units of biological diversity. Each species represents a distinct evolutionary lineage - free to take up different ecological niches, develop new morphological features or occupy a different geographic range.
To try an illustrate how diverse these unassuming little critters really are, I've put together a "treemap". In the plot below, each of the stained-glass window panels represents the number of species in one psocopteran genus, nested within a family (the heavier lines, with labels ending in -DAE) which in turn is nested within a suborder (the very heaviest lines, labeled -MORPHA). These higher taxonomic ranks are not fundamental units in the way species are. Even so, species placed within a taxonomic group share evolutionary history, and are united by particular morphological characters which they share. It turns out there are quite a few ways to be a bark louse:
And that's just bark lice!
For me, this chart is the best answer to "why?". How can you know you share the world with all this extraordinary diversity and not want to want to spend your time working out how it got here?
For me, this chart is the best answer to "why?". How can you know you share the world with all this extraordinary diversity and not want to want to spend your time working out how it got here?
*This is not a botany blog... I really have no idea what the tree is
Labels: bark lice, environment and ecology, psocoptera, sci-blogs, sunday spinelessness
Sunday, November 25, 2012
Sunday Spinelessness - An ID challenge
OK, here's a chance for the bug nerds to show off. A photo of a strange-looking beast I recently ran into:
The challenge to readers is to answer the two questions that went through my head when I first uncovered the creature (1) What the hell is that? (2) What's going with those opaque white projections?
Unlike others, I can't often you anything cool as a prize for being right, but surely an electronic record to your entomological know-how will be enough?
Labels: environment and ecology, mystery, photos, sci-blogs, sunday spinelessness
Sunday, November 18, 2012
Sunday Spinelessness - Shocked from sloth by a beautiful spider
Regular readers will know that I've been pretty slack in posting here in recent weeks. Just the same old boring reason - lots of "real" work to get done and, as much as I enjoy it, blogging necessarily floats to the bottom of TODO lists.
But I was shocked from my sloth this afternoon when I passed that accursed agapanthus and saw a spider I really had to share with the world:
It's an orb-weaving (araneid) spider, a relative of the familiar garden spiders like the very common Eriophora pustulosa that spin orb-shaped webs and catch unlucky flying insects. I can't be sure on the identification of this one, but I reckon (with some support from twitter's resided spider experts, [1], [2]) its a species a species of Novaranea. According to Ray and Lyn Foster's Big Spider Book New Zealand Novaranea species are most commonly encountered in in grasslands and tussocks, so perhaps this one blew in from the tall grass that covers some the abandoned gardens in our block.
However it made it our garden, I'm very happy to have encountered a such a neat looking spider, and even done a half-decent job capturing some of its beauty:
But I was shocked from my sloth this afternoon when I passed that accursed agapanthus and saw a spider I really had to share with the world:
It's an orb-weaving (araneid) spider, a relative of the familiar garden spiders like the very common Eriophora pustulosa that spin orb-shaped webs and catch unlucky flying insects. I can't be sure on the identification of this one, but I reckon (with some support from twitter's resided spider experts, [1], [2]) its a species a species of Novaranea. According to Ray and Lyn Foster's Big Spider Book New Zealand Novaranea species are most commonly encountered in in grasslands and tussocks, so perhaps this one blew in from the tall grass that covers some the abandoned gardens in our block.
However it made it our garden, I'm very happy to have encountered a such a neat looking spider, and even done a half-decent job capturing some of its beauty:
Labels: environment and ecology, photos, sci-blogs, sunday spinelessness
Sunday, June 3, 2012
Sunday Spinelessness - Nothing to see here
I'm off to the Transit of Venus Forum next week. I'm looking forward to meeting all sorts of clever and interesting people (and escaping the coming snow), but travelling and conferring won't leave much time for a few projects I really need to work on. So, today's blog post is going to have to be squeezed down to its smallest possible form (a queen ant that dropped in to read an early draft of my thesis last spring):
Labels: environment and ecology, phoning-it-in, photos, sci-blogs, sunday spinelessness
Sunday, May 27, 2012
Sunday Spinelessness - Even their eggs are spikey
I really like the leaf vein slugs (Athoracophoridae) that live in our garden and have featured here in the past. Here's the latest one to pass under my camera:
As much as I like them, I have to admit these guys are actually one of the more boring leaf vein slug species in New Zealand. Some of their relatives are much larger or more colourful and quite a few of them sport large wort-like growths (technically called papillae) that pattern their bodies in various ways. Te Ara and Soil Bugs both have galleries that let you get an idea of their diversity.
A couple of weeks ago I made a little discovery. Some of these slugs also have eggs that are covered in papillae
A couple of weeks ago I made a little discovery. Some of these slugs also have eggs that are covered in papillae
Not the greatest photo I'll admit. But it's hard work taking photographs in the dense New Zealand bush at the best of times, and I found these eggs in the low-growing cloud forest that covers the Leith Saddle on Mt Cargill. These are certainly slug eggs, so I did a bit of snooping among Astelia and ferns and other likely looking roosts for these nocturnal animals. I couldn't find any parents-in-waiting, but the ferns were utterly covered in what people that follow mammals might call "sign", so clearly there's a big population in the area.
Labels: environment and ecology, leaf veined slugs, photos, sci-blogs, science
Sunday, April 22, 2012
Sunday Spinelessness - What's brown and sticky?
Yup, I'm continuing with last week's theme of terrible jokes. Of course you know the punchline for this one, what's brown and sticky? A stick:
Both the objects in that photograph are brown and fairly sticky, but the one in the background is a bit more interesting.
That's not a stick - it's an insect doing a very convincing impersonation of a stick. Stick insects ( 'walking sticks' in North American, Phasmatodea everywhere in the world) are among the most impressive mimics in the biological world. As you can see, their bodies mirror the tiniest details of the plants they live on - right down to having stems and buds. The stickyness of stick insects goes deeper than their remarkable appearence - they also act like sticks. The rigid pose you see above is the result of my disturbing this one while trying to take a photo. The insect was so dedicated to its role I could easily pick it up and place it on its leaf while it maintained its spread-eagle pose.
A few minutes later it was on the move:
Both the objects in that photograph are brown and fairly sticky, but the one in the background is a bit more interesting.
That's not a stick - it's an insect doing a very convincing impersonation of a stick. Stick insects ( 'walking sticks' in North American, Phasmatodea everywhere in the world) are among the most impressive mimics in the biological world. As you can see, their bodies mirror the tiniest details of the plants they live on - right down to having stems and buds. The stickyness of stick insects goes deeper than their remarkable appearence - they also act like sticks. The rigid pose you see above is the result of my disturbing this one while trying to take a photo. The insect was so dedicated to its role I could easily pick it up and place it on its leaf while it maintained its spread-eagle pose.
A few minutes later it was on the move:
I don't know what species we are looking at here. There are about 20 named species in New Zealand, though that is probably an underestimate of the true diversity. There seems to be lots of interesting biology going on among those species - species with sexual and asexual populations, a genus that arose by hybridisaton and one genus known only from two specimens. It's possible this one is Niveaphasma annulata - a species that has patchy distribution across much of the southern half of the South Island and is pretty common in and around Dunedin. What ever the species name, here's the beast making a bid for freedom from the faked-up leaf litter I put together for this little photo-shoot:
Labels: environment and ecology, sci-blogs, stick insect, sunday spinelessness
Sunday, April 8, 2012
Sunday Spinelessness - Molluscan mausoleum
Going way back today, to a photo I took about 6 years ago:
This is from the high tide mark at Aramoana, and the shells that dominate the little assemblage are Zethalia zelandica - the New Zealand wheel shell. I don't have anything particularly important or meaningful to say about these shells. I was just struck by the diversity of the patterns and colours that they bear, and the concentration of shells into a relatively small stretch of a relatively large beach. Zethalia live in sandy conditions and somewhat deep water, so the shells presumably washed in from the harbour and had collected over time at a point at which the waves and currents coalesce.
This is from the high tide mark at Aramoana, and the shells that dominate the little assemblage are Zethalia zelandica - the New Zealand wheel shell. I don't have anything particularly important or meaningful to say about these shells. I was just struck by the diversity of the patterns and colours that they bear, and the concentration of shells into a relatively small stretch of a relatively large beach. Zethalia live in sandy conditions and somewhat deep water, so the shells presumably washed in from the harbour and had collected over time at a point at which the waves and currents coalesce.
Labels: Dunedin, environment and ecology, photos, sunday spinelessness, zethalia
Sunday, March 18, 2012
Sunday Spinelessness - Gotcha!
I only have moment to spare today, so I thought I'd share a life and death moment from the garden.
The fearsomely-spiked creature photographed above is the larva of a ladybird (that is, a beetle of the family Coccinellidae), specifically the New Zealand and Australian native species Apolinus lividigaster. It's meal is an ahpid, though I couldn't tell you which species.
Learning that ladybirds are vicious predators (adults have more or less that same tastes as their larvae) might go some way to undermine ladybirds' status as a "cute" insect that escapes the "yuck" reaction so many of their kin seem to evoke. But it's worth remembering that ladybirds are very useful. Most species specialise in eating plant-sucking insects like aphids and scales, and so can be a boon to gardeners. On a larger scale, predatory ladybirds are often introduced as "biological" control to help keep pest numbers low.
Learning that ladybirds are vicious predators (adults have more or less that same tastes as their larvae) might go some way to undermine ladybirds' status as a "cute" insect that escapes the "yuck" reaction so many of their kin seem to evoke. But it's worth remembering that ladybirds are very useful. Most species specialise in eating plant-sucking insects like aphids and scales, and so can be a boon to gardeners. On a larger scale, predatory ladybirds are often introduced as "biological" control to help keep pest numbers low.
Labels: beetle, coccinellidae, environment and ecology, photo, sci-blogs, sunday spinelessness
Sunday, February 26, 2012
Sunday Spinelessness - They're alive!
It would take the most dedicated reader of The Atavism to remember the empty snail shell I wrote about last year. I'll admit even I'd mainly forgotten about myself, but this weekend I went on a little mini-field trip to collect a few samples for a colleague's ongoing project. In planning that trip I did remember the slightly mysterious shells I found last winter, and so decided to head back and see if I could get a few more to send along an an expert who might be able to put a name to them.
Sure enough, I found plenty more empty shells in different states of aging , but deep within the leaf litter I also uncovered one shell that was still playing house to an animal. I couldn't quite be sure there was a healthy animal in the shell when I first picked it up, since the snail was already retracted inside. Thhe easiest way to encourage a sleeping snail out from its shell is to warm in up, so I clasped it in my palm for about a minute and, well, here's the result:
Obviously, having taken the photographs I put this snail back under the nice moist leaf litter from which I'd taken it. Since then I've done a bit of research and I'm fairly confident that I've now identified this population down to genus level. But I've wrong about these things before (most recently by en entire superfamily...) so I'm still going to send the empty shells I collected from the same site to someone who has much more expertise than I do. I'll keep you updated on just exactly what these creatures are.
Labels: Dunedin, environment and ecology, molluscs, native snails, photo, sci-blogs, snails, sunday spinelessness
Sunday, February 12, 2012
Sunday Spinelessness - A fly in the bee garden
Just a couple of photos today.
We planted a bee garden this year - Borage, Phacelia foxglove and a couple of other plants that are known to attract honey bees and and their bumbling cousins into the garden:
The "bee garden" has worked - there is hardly a moment during the day when there isn't at least one bee making it's way around the little patch of garden. I'll show you some photos of them soon, but today I wanted to share a much smaller creature. A tiny fly perched on the leaf of a chickweed (Stellaria):
I'm terrible with fly taxonomy (or flylogeny if you'd rather) - I like to think I can at least get most of the spiders and insects I encounter down to the family level (roughly equivalent to successfully identifying myself as a great ape). With the exception of a few groups - crane flies, robber flies and hover flies, I get nowhere with flies. And so it is with this one, all I can tell you is that it's small (~3mm) probably from group called Schizophora. And that I quite like this photo.
We planted a bee garden this year - Borage, Phacelia foxglove and a couple of other plants that are known to attract honey bees and and their bumbling cousins into the garden:
The "bee garden" has worked - there is hardly a moment during the day when there isn't at least one bee making it's way around the little patch of garden. I'll show you some photos of them soon, but today I wanted to share a much smaller creature. A tiny fly perched on the leaf of a chickweed (Stellaria):
I'm terrible with fly taxonomy (or flylogeny if you'd rather) - I like to think I can at least get most of the spiders and insects I encounter down to the family level (roughly equivalent to successfully identifying myself as a great ape). With the exception of a few groups - crane flies, robber flies and hover flies, I get nowhere with flies. And so it is with this one, all I can tell you is that it's small (~3mm) probably from group called Schizophora. And that I quite like this photo.
Labels: diptera, environment and ecology, photos, sci-blogs, sunday spinelessness
Sunday, February 5, 2012
Sunday Spinelessness - King of the castle
A moment of life in the undergrowth captured (leaf beetles playing king of the castle?):
I don't know exactly what was going on here, though I've got my ideas. Whatever I saw, it involved a lot of wild antennae-shaking from the two beetles facing each other and apparently very little interest in proceedings from the base of the "short, blunt beetle-pyramid".
I don't know exactly what was going on here, though I've got my ideas. Whatever I saw, it involved a lot of wild antennae-shaking from the two beetles facing each other and apparently very little interest in proceedings from the base of the "short, blunt beetle-pyramid".
Labels: beetle, environment and ecology, photos, sci-blogs, sunday spinelessness
Sunday, January 29, 2012
Sunday Spinelessness - We have bees
If I asked you to think of a bee I'm willing to bet you'd come up a with picture of a honey bee: a fuzzy little creature with yellow and black stripes and a rear end that can deal damage. Perhaps you'd think of a big fat bumblebee making its way between garden flowers, or, if you are lucky enough to live near them, some commercially important pollinator like a mason bee. Even if we including those extra forms in the way we think about bees, we are only taking a tiny sampling of the twenty thousand species that make the superfamily Apoidaea.
There are giant sex-crazed killer-bees, and tiny bees that specialise in gathering nectar from the false-flowers of Euphorbia. Bees that form colonies with thousands of adults, and bees that keep to themselves. There are hairy bees, and hairless bees, bees that specialise in stealing honey from other bees and bees that develop "soldiers" who give their lives to fight these would-be thieves off. There are even bees that eat meat. Given the huge number of ways there are to be a bee, you might ask what unites this group. Bees (like ants) are specialised wasps. They all descend from a group of wasps that gave up a typical waspish lifestyle, providing insect or spider flesh for their young while using nectar to fuel their activities as adults, and instead started provisioning their larvae with nectar and pollen. From so simple a switch the seemingly endless forms of bee have arisen.
It might come as a surprise to New Zealanders that we have native bees. Our natives aren't hugely important pollinators of commercial crops, in fact, long-tongued bumblebees were introduced for just this reason. Though our bees pollinate plenty of native plants, they don't play as large role in plant reproduction as their relatives in some eco-systems - birds, beetles, butterflies, lizards true files and bats are all important pollinators in New Zealand natural habitats (and introduced rats have partly replaced declining bats in this role). But the 30 or so native bee species that we know about (there could well be more) are still part of our natural heritage, and what's more, they are a part that goes unnoticed under many of our noses - as a few species can do quite well in suburbia. The locals come in two of the nine recognised bee families , so let's treat each seperately.
Colletidae (plasterer bees)
The colledtids are called "plasterer bees" because they smooth-off the walls of their nests with a secretion that create with their mouths. In New Zealand we have 18 large-ish (up to 12mm) species in Leioproctus and another 9 or so Hylaeus species. The spur for me writting this post was encountering a member of the South Island species Le. fulvescens sitting in our hallway last weekend (duly photographed and moved off to the garden).
Le. fulvescens is the only native bee that fufills the yellow black and fuzzy sterotype for bees. The others are black and relatively hairless. Bees often specialise on collecting pollen and nectar from a particular group of flowers, and most New Zealand colledtids search for flowers from the Myrtle family (e.g. rātā, pōhutukawa, mānuka and kānuka). I've never stopped to watch them, but I gather that native bees can outnumber introduced ones on these flowers at the right time of the year. A few other colledtids, including Le. fulvescens, prefer flowers (native and introduced) from the family Asteraceae (daisies, sunflowers and their kin). I'd like to think the the one photographed above had been brought into our garden by the display the federation daises are putting on - but the hawkbit taking over the less acessable regions of the section is a probably a more likely source.
These bees all produce nests in the soil, and when the conditions are right females can lay an egg and provision a nest with nectar at the rate of one per day. The clay bank that our house sits under is full of little drilled holes, which I'm sure mark the start of Leioproctus nests. They're most abundant towards the start of summer (November-December) but they'll hang around until February when the last generation of females will find somewhere to hide over the winter.
Le. fulvescens is the only native bee that fufills the yellow black and fuzzy sterotype for bees. The others are black and relatively hairless. Bees often specialise on collecting pollen and nectar from a particular group of flowers, and most New Zealand colledtids search for flowers from the Myrtle family (e.g. rātā, pōhutukawa, mānuka and kānuka). I've never stopped to watch them, but I gather that native bees can outnumber introduced ones on these flowers at the right time of the year. A few other colledtids, including Le. fulvescens, prefer flowers (native and introduced) from the family Asteraceae (daisies, sunflowers and their kin). I'd like to think the the one photographed above had been brought into our garden by the display the federation daises are putting on - but the hawkbit taking over the less acessable regions of the section is a probably a more likely source.
These bees all produce nests in the soil, and when the conditions are right females can lay an egg and provision a nest with nectar at the rate of one per day. The clay bank that our house sits under is full of little drilled holes, which I'm sure mark the start of Leioproctus nests. They're most abundant towards the start of summer (November-December) but they'll hang around until February when the last generation of females will find somewhere to hide over the winter.
Halictidae (sweat bees)
The halicitids get their scientific and their common name from the fact they are attracted to the salt in human sweat. This family is represented in New Zealand by 4 or 5 species of Lasioglossum, with one, La. sordum common in disturbed habitats. I've only ever seen one of these bees moving about between flowers, but must have scooped hundreds of them out of the my parent's swimming pool in the Wairarapa. I don't know if the chlorine salts that balance the pool's chemistry set them off, if they're thirsty or if the polarised blue light that shines off the water plays tricks with their eyes, but something about the pool leads to a fatal attraction.
Scooping these guys out of the pool let's you learn a little about them, first, the males are substantially smaller and thinner waisted than the females and second, the females are capable of delivering a very small sting. Steven O. Schmidt, an entomologist who has evidently been stung by most of the venomous insects in the world , has created an index to measure the power of an insects sting. The sweat bee scores lowest on the Schmidt Pain Index - a 1.0 with the desctiption "Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm". Certainly nothing compared with the pain of the tarantula hawk (relatives of the spider-hunting wasp featured here), which weighs in at 4.0 and is "blinding, fierce, shockingly electric...". Lasioglossum seem's to live up to its famaly's reputation - it took me a little while to convince myself that I had just been stung (by a creature who's life I was trying to save no less!) and it does feel a little bit like a spark fading out on your skin.
The time it takes for a water-logged bee to get back to being airworthy also gave me a chance to take a few photos - you can tell these are staged because this is exactly the sort of flower (requiring a long tongue to get the sweet reward) that a native bee would never visit!
In terms of their habits, our native halicitids are much less fussy than the colledtids - they've been recorded from at least 80 species of plants across many families. This undemanding approach to life might be a result of their longer lifecycle - females start emerging as soon as August, the first males appear around November and both sexes will persist until frosts send them into dormancy (I don't know of any records from Northland, but bumblebees can keep year-round colonies up there, and these bees could conceivable survive the winter their too. Lasioglossum are described as solitary, but, although they don't form huge colonies, there is evidence that female La. sordum will share nest entrances. Such behaviour is probably one part of a continuum that goes from solitary behavior, through to shared provisioning of nests and on to super-colonies like those of honey bees (and some sting-less bees). Both the behaviour (provisioning of nests with honey, a food that can be stored) and the genetics (a form of sex determination that means sisters are effectively more closely related to each other than they are to their mothers) of bees open the door to evolution of "true social" behaviour, and the steps along the way provide scientists with rich ground to test their ideas about this evolutionary phenomenon.
That's it really. Next time you're see some bare soil in a nice flowery habitat, why don't you look and see if you can find some perfectly cyclindrical holes (and piles of soil beside). Or better yet, spend a little time in the garden and see if you can't spot a native bee making its way from flower to flower.
Check out Te Ara's article on native bees here, and the source of most of the information above:
Donovan, B.J. (1980).Interactions between native and introduced bees in New Zealand [pdf]. NZ Journal of Ecology 3:104-116.
Scooping these guys out of the pool let's you learn a little about them, first, the males are substantially smaller and thinner waisted than the females and second, the females are capable of delivering a very small sting. Steven O. Schmidt, an entomologist who has evidently been stung by most of the venomous insects in the world , has created an index to measure the power of an insects sting. The sweat bee scores lowest on the Schmidt Pain Index - a 1.0 with the desctiption "Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm". Certainly nothing compared with the pain of the tarantula hawk (relatives of the spider-hunting wasp featured here), which weighs in at 4.0 and is "blinding, fierce, shockingly electric...". Lasioglossum seem's to live up to its famaly's reputation - it took me a little while to convince myself that I had just been stung (by a creature who's life I was trying to save no less!) and it does feel a little bit like a spark fading out on your skin.
The time it takes for a water-logged bee to get back to being airworthy also gave me a chance to take a few photos - you can tell these are staged because this is exactly the sort of flower (requiring a long tongue to get the sweet reward) that a native bee would never visit!
In terms of their habits, our native halicitids are much less fussy than the colledtids - they've been recorded from at least 80 species of plants across many families. This undemanding approach to life might be a result of their longer lifecycle - females start emerging as soon as August, the first males appear around November and both sexes will persist until frosts send them into dormancy (I don't know of any records from Northland, but bumblebees can keep year-round colonies up there, and these bees could conceivable survive the winter their too. Lasioglossum are described as solitary, but, although they don't form huge colonies, there is evidence that female La. sordum will share nest entrances. Such behaviour is probably one part of a continuum that goes from solitary behavior, through to shared provisioning of nests and on to super-colonies like those of honey bees (and some sting-less bees). Both the behaviour (provisioning of nests with honey, a food that can be stored) and the genetics (a form of sex determination that means sisters are effectively more closely related to each other than they are to their mothers) of bees open the door to evolution of "true social" behaviour, and the steps along the way provide scientists with rich ground to test their ideas about this evolutionary phenomenon.
That's it really. Next time you're see some bare soil in a nice flowery habitat, why don't you look and see if you can find some perfectly cyclindrical holes (and piles of soil beside). Or better yet, spend a little time in the garden and see if you can't spot a native bee making its way from flower to flower.
Check out Te Ara's article on native bees here, and the source of most of the information above:
Donovan, B.J. (1980).Interactions between native and introduced bees in New Zealand [pdf]. NZ Journal of Ecology 3:104-116.
Labels: bees, coletidae, environment and ecology, halicitidae, native bees, photos, sci-blogs, sunday spinelessness
Sunday, January 22, 2012
Sunday Spinelessness - For Ted
As I said last week, I've just returned from a bit of a summer holiday. I'm not the sort of person who can do absolutely nothing for any length of time, so I tend to find my relaxation in doing things that I wouldn't have a chance to if I was at home.Like riding a mountain bike. As far as I'm concerned, the best place in Dunedin is the top of Sandymount, an eroded volcanic cone that marks the start of the descent from Highcliff down to Portobello when you ride the Otago peninsular*. I could get all lyrical about the feeling of being away from the rest of the world, or the joy of the moment that you roll from the stiff climb into the fast and flowing descent, but thankfully Brian Tuner has already written a poem about my favourite bike ride:
When I spend time at my parent's house in the Wairarapa I leave my road bike behind and borrow my dad's old mountain bike to explore some slower, bumpier rides. That's how I ended up, in the middle of a mid-summer day, struggling my way up a crushed limestone path in a small reserve in Masterton. Bike riding is one of the past times that had to give way when my thesis ate all my spare time, so this really was a struggle. Even riding in the lowest gear I could, I soon gave up on the nice "upright" form that helps a rider spin their way up a hill and instead grovelled my way up, shoulders slumped and head down. And that was a good thing, because with my eyes pointing down I spotted a small creature, seeming to hover just above the ground as it zoomed out across the path, .The creature stopped, turned a few degrees, sprinted down the path a little and stopped again. So I stopped, not, of course, because I needed a break from the hill, but because I've read Ted MacRae's blog long enough to recognise the behaviour playing out in front of me.
If you like bugs and you don't read Ted's blog (Beetle's in the Bush) then you really ought to fix that oversight. He's a great photographer and an immensely knowledgeable entomologist, but the thing that really springs from Ted's posts is a love for natural history. Tiger beetles are one of the bits of natural history that Ted loves the most, and its through his photos and posts that I've been introduced to these wonderfully rapacious critters. Tiger beetles live almost everywhere on earth. New Zealand plays hosts to a small radiation (12 species, all arising in the last 10 million years, Pons et al. 2011, doi: 10.1016/j.ympev.2011.02.013s) and, although they aren't particularly rare, I'd never seen one before this day. So I scooted a little closer, and the beetle (raised up from the ground by slender legs, and not actually hovering above it) sprinted a little further. And so it went: scoot. sprint. scoot, sprint, until I got within a metre or so and the beetle added "fly" to its repertoire and disappeared into the long grass.
I was happy just to have at last seen one of our tigers, but I wanted to get a little closer and even see if I could grab a photo of the skittish creature. So that evening I drove out to the reserve and walked along the paths at the top of the hill, hoping to see another beetle zoom into view. A couple of laps of those tracks yielded nothing. If you want to see something interesting the best bet is stop and let the world happen around for you for a little bit, so I stopped. Before long I was watching native (Lasioglossum) bees investigating nesting sites on the ground and then, out of the corner of me eye: Sprint. Stop. Sprint.
Neocicindela tuberculata is the most widespread of our tiger beetles, and an ecological generalist that copes with disturbed habitats as well as beaches, riverbanks and forests. Like tiger beetles everywhere, they are predators that use their bursts of speed to hunt down smaller insects. The harsh light, the beetle's shininess and my lack of photographic skills didn't combine all that favourably, but I did get a few headshots that let you get an idea of what happens to a prey item once a tiger beetle has caught it:
I'm not sure, but I think the protuberance you can see in these photos may be an ovipositor - an organ used for laying eggs. These beetles lays their eggs in burrows, and the larvae that develop in them are every bit as fearsome looking as the elders. Since it seemed like this beetle might in the process of keeping this population going, I decided I should let her get on her way while I could be satisfied with a beetle I'd long wanted to see marked off my "life list". The only problem with being a invertebrate fancier is that makes it another one down, approximately 10 million to go!
* At least it is if you don't find yourself stuck behind a camper van trundling down the skinny road at 20 kph!
...
I push the gear
down a little and the chain
drops onto a small sprocket
and the wheels start to spin
faster, and the air's
like a quick tongue
in my hair as I descend
swinging in wide curves
around the hill...
Training on the Peninsular
down a little and the chain
drops onto a small sprocket
and the wheels start to spin
faster, and the air's
like a quick tongue
in my hair as I descend
swinging in wide curves
around the hill...
Training on the Peninsular
When I spend time at my parent's house in the Wairarapa I leave my road bike behind and borrow my dad's old mountain bike to explore some slower, bumpier rides. That's how I ended up, in the middle of a mid-summer day, struggling my way up a crushed limestone path in a small reserve in Masterton. Bike riding is one of the past times that had to give way when my thesis ate all my spare time, so this really was a struggle. Even riding in the lowest gear I could, I soon gave up on the nice "upright" form that helps a rider spin their way up a hill and instead grovelled my way up, shoulders slumped and head down. And that was a good thing, because with my eyes pointing down I spotted a small creature, seeming to hover just above the ground as it zoomed out across the path, .The creature stopped, turned a few degrees, sprinted down the path a little and stopped again. So I stopped, not, of course, because I needed a break from the hill, but because I've read Ted MacRae's blog long enough to recognise the behaviour playing out in front of me.
If you like bugs and you don't read Ted's blog (Beetle's in the Bush) then you really ought to fix that oversight. He's a great photographer and an immensely knowledgeable entomologist, but the thing that really springs from Ted's posts is a love for natural history. Tiger beetles are one of the bits of natural history that Ted loves the most, and its through his photos and posts that I've been introduced to these wonderfully rapacious critters. Tiger beetles live almost everywhere on earth. New Zealand plays hosts to a small radiation (12 species, all arising in the last 10 million years, Pons et al. 2011, doi: 10.1016/j.ympev.2011.02.013s) and, although they aren't particularly rare, I'd never seen one before this day. So I scooted a little closer, and the beetle (raised up from the ground by slender legs, and not actually hovering above it) sprinted a little further. And so it went: scoot. sprint. scoot, sprint, until I got within a metre or so and the beetle added "fly" to its repertoire and disappeared into the long grass.
I was happy just to have at last seen one of our tigers, but I wanted to get a little closer and even see if I could grab a photo of the skittish creature. So that evening I drove out to the reserve and walked along the paths at the top of the hill, hoping to see another beetle zoom into view. A couple of laps of those tracks yielded nothing. If you want to see something interesting the best bet is stop and let the world happen around for you for a little bit, so I stopped. Before long I was watching native (Lasioglossum) bees investigating nesting sites on the ground and then, out of the corner of me eye: Sprint. Stop. Sprint.
Neocicindela tuberculata is the most widespread of our tiger beetles, and an ecological generalist that copes with disturbed habitats as well as beaches, riverbanks and forests. Like tiger beetles everywhere, they are predators that use their bursts of speed to hunt down smaller insects. The harsh light, the beetle's shininess and my lack of photographic skills didn't combine all that favourably, but I did get a few headshots that let you get an idea of what happens to a prey item once a tiger beetle has caught it:
I'm not sure, but I think the protuberance you can see in these photos may be an ovipositor - an organ used for laying eggs. These beetles lays their eggs in burrows, and the larvae that develop in them are every bit as fearsome looking as the elders. Since it seemed like this beetle might in the process of keeping this population going, I decided I should let her get on her way while I could be satisfied with a beetle I'd long wanted to see marked off my "life list". The only problem with being a invertebrate fancier is that makes it another one down, approximately 10 million to go!
* At least it is if you don't find yourself stuck behind a camper van trundling down the skinny road at 20 kph!
Labels: beetle, Cicindelinae, environment and ecology, photos, sci-blogs
Sunday, January 15, 2012
Sunday Spinelessness - 2012
Alright, it's time to break out from the post-thesis/ Christmas holiday / summertime lethargy that this blog, and its writer, have sunk into and get properly started with 2012.
Following tradition*, I'll start the year with further proof that the lol-fauna of science blogs is entirely more diverse than that of any other corner of the internet. A nymph of the New Zealand praying mantis (Orthodera novaezealandiae or whē) eyeing up the photographer from an anemone leaf in my parents' garden (thanks to Rafael maia (@hylopsar) for the idea).
*Well, it's happened twice now.
Following tradition*, I'll start the year with further proof that the lol-fauna of science blogs is entirely more diverse than that of any other corner of the internet. A nymph of the New Zealand praying mantis (Orthodera novaezealandiae or whē) eyeing up the photographer from an anemone leaf in my parents' garden (thanks to Rafael maia (@hylopsar) for the idea).
*Well, it's happened twice now.
Labels: environment and ecology, mantids, Orthodera novaezealandiae, 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, 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
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