It seems Gareth Morgan has declared a war on cats. It will, I'm sure, come as a great surprise to you that Morgan's description of cats as ruthless and sadistic killers that we must eventually purge from the land  has met some opposition. Invoking outrage is pretty good way to get free advertising in New Zealand, and if you measure the campaign's success in tweets, comments and talkback calls I guess Morgan is on to a winner. But I'd like to think we can do better than simply setting up an argument between supporters of Morgan's Maoist purge and cat lovers who think their moggie can do no harm.

Cats are a problem

Most of the reaction to Morgan's campaign has been to basically treat it as a joke. We should be clear then, that introduced predators are the number one threat to New Zealand species. Stoats, weasels possums and rats all contribute the decline of birds and lizards (and invertebrates, though we don't monitor those species closely enough to track their progress). Cats are certainly part of that problem. They have contributed to the extinction of at least 6 bird species  in New Zealand, and many more populations and subspecies have been lost partly as a result of predation by cats (Merton, 1978). Cats continue to pose a threat to our wildlife. The impact of feral cats on shorebirds  (plovers, dotterels, oystercatchers) and kakapo is well documented (Karl and Best, 1981 doi: 10.1080/03014223.1982.10423857). In the space of a week one cat managed to kill 102 native short tailed bats.

The problem isn't restricted to wild cats. Pet cats will attack and kill native birds and lizards when they have the chance. In Dunedin the impact of tame cats is large enough that it's been estimated local bird populations (including natives) wouldn't survive if they weren't replenished by migrants from around the fringes of the city (van Heezik, et al. 2010. doi: 10.1016/j.biocon.2009.09.01)

Getting rid of cats isn't necessarily a solution

It's clear then, that cats are a problem for the conservation of native wildlife. But it's not nearly as clear that simply getting rid of cats will be much help. Every study of the diet of cats in New Zealand has found that cats kill a lot of mice and rats. These rodents are themselves predators of birds so removing one predator from our country may simply let another run amok. When feral cats were removed from Little Barrier island it led to an outbreak in kiore (Pacific rat), which threatened Cook's Petrel populations on that island (Rayner et al, 2007 avaliable via PMC ).

Should we phase out cats in New Zealand?

So, if Morgan's plan was actually do-able, should we do it? I have to honest here and tell you, I don't know. It's abundantly clear that cats, both feral and domestic, can kill native animals. It's clear that in at least some cases that killing can have a major impact on populations, but removing cats might not help all that much. If you want to know whether the impact of your typical urban moggy justifies Morgan's campaign, especially given the abundance of rats in New Zealand, you'd have to ask a conservation biologist. That's something no news organization has bothered with yet, as far as I can tell.

Is this the conversation we should have started?

It's fairly obvious that Morgan's website, with its strange anthropomorphism (cats are predators sure, sadists? no) was designed to draw headlines and "start conversations". But what hope is there for environmentalists in conversation where our side wants to take people's kittens away?

Introduced predators are the biggest threat to New Zealand's biodiversity, so the goal of eventually controlling these predators so tightly that they no longer pose a threat is a very worthy one. But the sort of change required to get us from today, where only 12% of the conservation estate is managed for predators, to that goal has to come from the ground up. Picking fights like this will get you headlines, but I don't think it will change anyone's mind.

Labels: cats, conservation, new zealand, sci-blogs, science, science and society

Markus Pfenninger and his colleagues asked just that question by looking at snails from the Northern Hemisphere genus Trochulus (doi: 10.1186/1471-2148-5-59). This genus contains many species that sport very fine and soft hairs. Pfenninger et al.collected ecological data for each species, and used DNA sequences to estimate a the evolutionary relationships between those species. From these data, they were able to infer the common ancestor of modern Trochulus species was probably hairy, and three separate losses of hairyness can explain all the among-species variation in this trait. Moreover, it appears the loss of hairs in Trochulus is associated with a switch for wet to dry habitats. Given this finding, Pfenninger's team hypothesised that, in Trochulus at least, hirsute snails might stick to host plants more effectively than their bald brethren. Indeed, in experiments it took more force to dislodge a hairy shell from a wet leaf than non-hairy one.

Labels: molluscs, native snails, new zealand, sci-blogs, science, sunday spinelessness

I was going to start this post by saying taxonomy has a language of its own, but that's not really true. Taxonomy just has a whole lot of Latin. When I've given talks in schools, I've almost always been asked why scientists insist on giving creatures those strange Latinised names. The answer is, we need names that anyone anywhere can recognise and pin to particular species or group. A common name like "black bird" might make sense in conversation in New Zealand, but in other circumstances it could refer to a single species (Turdus merula), the five species that make up Turdus, or a whole bunch of species in the new world family Icteridae. When taxonomy really got started Latin was the language which scientists from different countries used to speak to each other, so modern taxonomy follows Linnaeus in using Latinised names.

But the Latin terms used by taxonomists don't stop with names, if you thought they were difficult to understand you should open a taxonomic work. The first time I did I was lost in a sea of lecto-, neo- and allo-types; homonyms junior and senior and Nomina nuda, obltum and protectum. The title of this post, Incertae sedis is another of those strange taxonomic terms and translates as "uncertain placement". Most big taxonomic reviews include a few species the author is certain are well defined, but hard to place into a higher group. Those species get placed under the heading Incertae sedis.

I used that title because today's subject is... a land snail... of some sort

I found this guy (actually, all land snails are hermaphrodites, so I need a better familiar term for them) in our garden and it's pretty tiny (this is a 50 cent coin, almost exactly the same size as a quarter for North American readers):

Labels: environment and ecology, molluscs, new zealand, photos, sci-blogs, sunday spinelessness

New Zealand has spoken, the kākāriki is our newest Bird of the Year. It took a late surge to push the slender parrot past the other main contender for the prize, the pukeko, but in the end the kākāriki won a clear majority and it's time for the nation to celebrate these endangered birds.

New Zealanders are rightly proud about some of the weirder creatures that call our islands home. Our native wrens, frogs, tuatara, large parrots and kiwi are all examples of ancient lineages found in New Zealand and nowhere else in the world. These species, and our geological origins, have formed part of New Zealand's creation myth - a country that went its own way 85 million years ago and has been doing its own thing ever since. The kākāriki don't fit in that narrative. Instead, theses parrots connect New Zealand's biota to the Pacfic and serve to highlight the way the recent geological and climatic history of our islands has shaped the creatures we share them with.

When we say kākāriki we are actually talking about three species of small parrot, each native to New Zealand. There had been considerable debate among ornithologists about whether the different forms, which are most easily differentiated by the colour of a patch of feathers on their forehead, really represent different species rather than variants of a single species. In 2001 Wee Ming Boon, then a PhD student at Victoria University in Wellington provided the answer. Molecular data showed that each of these forms are distinct from each other.

When Europeans first arrived in New Zealand all the kākāriki species were relatively common in beech forests. So much so that when the beech failed to set enough seed for the parrot populations they would invade the settler's farms and orchids. Robert Fulton, speaking to the members of the Otago Insitute in 1907, noted how the birds which had been "shot in their thousands" only thirty years before had all but disappeared. (The Otago Witness also recorded Dr Fulton's sentiment that the way Kererū were slaughtered in the province put Otago-ites on "the same level as the Spanish and the Mexicans") . Today all three species are endangered, deforestation and the introduction of mammalian predators like the stoat being a much more to blame than early orchardists. The yellow fronted species is still relatively widespread, whereas the red fronted is extinct on the mainland and the orange fronted is restricted to few small pockets of beech forest in the South Island and there may be as few as 50 birds left.

All three species are in the genus Cyanoramphus, which has representatives stretching from Raiatea in the Society Islands all the way down to Macquarie Island in the sub-antarctic. The same sort of molecular evidence that was sued to establish species status for the various kākāriki can be used to establish relationships between them and their Pacific cousins. The New Zealand species are most closely related to a species from New Caledonia. Using a molecular clock analysis, Boon and colleagues could show that modern populations of kākāriki on New Zealand and the Chatham Islands descend from a single invasion of our country from the Pacific, most likely from New Caledonia, within the last five hundred thousand years. Interestingly, the three New Zealand species split even more recently than that. It seems seems populations of kakariki become isolated within pockets of beech forests that survived the last ice age. Seperated in this way, populations would become become independently evolving lineages, which in turn can come species.

It might seem that recent arrivals like the kākāriki aren't quite as uniquely New Zealand a group of birds as those ancient and odd birds like the kakapo and the kiwi. But, as we've been able to apply molecular tools to more and more of the plants and animals we share our islands with it's become increasing clear that recent arrivals far out number the old timers. In fact, in many ways the kākāriki is a perfect example of the way life has evolved in New Zealand . It's been here for only a short while, but in that time the turbulent geological and climatic history has shaped these birds in a unique way. So, apart from being very handsome parrots indeed, the kākāriki are worthy holders of the title of Bird of the Year. Now let's just make sure we get to keep some of these birds in our forests!

Labels: bird of the year, evolution, kakriki, new zealand, sci-blogs

New Zealanders often think of our unique biota as a sort of time capsule - a glimpse at lifeforms that have long since been extinguished in other parts of the world. New Zealand has been apart from the rest of the world for 85 million years. At that time the land that makes up our mini-continent split from the super-continent Gondwana, opening up the Tasman Sea and moving northward . A land apart from the rest of the world. Until recently most scientists have thought that the subset of the Gondwanan flora and fauna that set sail on that proto-New Zealand was likewise on its own evolutionary trajectory -insulated from biological happenings in the rest of the world. The idea of the New Zealand biota as a group of refugees from an ancient ecosystem hanging onto "Moa's Ark" has become part of the New Zealand psyche.

In recent years Moa's Ark has sprung more than a few leaks. Icons of our Gondwanan heritage like Nothofagus beech trees have been shown to be recent arrivals. Geologists have suggested the whole continent submerged 20 million years ago, drowning any refugees still on board, and now new research suggests even the most unlikely of immigrants - the giant, flightless moa - may have arrived in New Zealand well after we left Gondwana.

The group of birds to which the moa belonged, the ratites, have long fascinated evolutionary biologists. All the ratites are flightless (though, as we'll see they are related to the quail-like tinamous which can fly passably well) and all the major landmasses that had their start in Gondwana had at least one ratite species before humans arrived on the scene. Africa has ostriches, South America the rhea, Australians have emus and cassowary, Madagascar had the Elepahant bird and New Zealand lost the moa but retains the kiwi. The far flung distribution of the ratites and their apparent lack of ability to disperse between continents has led to them being put forward as a classic example of an idea called vicariance biogeography in which the evolutionary history of a group is driven by the geological history of the land on which they live.

For vicariance biogeographers the evolution of the ratites was driven by the movement of the continents. The ancestor of all modern ratites was a flightless bird living in Gondwana and as each new continent split and rifted away from the super continent it took with it a population of ratites which adapted to the ecological changes brought on by their continent's journey: cassowaries in the Wet Tropics of Australia, ostriches on the African Savannah, rhea on the Pampas. It's certainly a nice story, but science has a way of ruining nice stories. The role of vicariance of evolution in the ratites was put to the test once we became able to use molecular evidence to reconstruct the relationships between species. If the geologically driven sketch of ratite evolution I presented above is right then the pattern of branching we find among ratites from different continents should match the order in which we know the continents broke up, something like this:

In 2001 Alan Cooper and colleagues sequenced the entire mitochondrial genome (some 12 000 bases of DNA) from representatives of each of the extant ratites and, remarkably, two species of moa. The long, careful process of retrieving DNA sequences from sub-fossil bones deserves a post of its own but for the sake of this article we only need to know what Cooper et al found when they used that DNA to recover the the relationships between ratite species.

The species in bold text above don't fit the pattern that we'd expect from geology alone. If ratite relationships simply reflected the Gondwanan breakup we'd expect to see ostriches grouping with rheas (and apart from the other ratites). New Zealand's two ratite orders are even more surprising, the kiwi lineage is more closely related to the Australian ratites than it is to the moa species. When combined with a molecular clock analysis Cooper et al. concluded that modern kiwis are the descendants of ancient immigrants hailing from either Australia or islands in the Lord Howe Rise (which have since submerged). In order to explain that trans-tasman dispersal the authors reached for the last resort of the desperate biogeographer and invoked a land bridge for which there is little geological evidence. In fact, as we'll see it now seems more likely that the ancestors of the kiwi and the moa flew to New Zealand.

Even with the mitochondrial phylogeny of the group published there was considerable room for uncertainty in how the ratites related to each other. The underlying shape of ratite tree makes it particularly difficult to accurately recover with phylogenetic methods. When we use DNA sequences to estimate a phylogenetic tree we need to find species that share mutations that have accrued during the evolution of the group we're looking at. The branches that relate the different ratite species are relatively short, so there was little time for mutations that set related groups apart from more distantly related ones to accrue. Even worse, the branches that reach to the modern species (the tips of the tree) are very long meaning there has been a lot of time to any mutations that did accrue in those critical short branches to be overwritten*. There are three approaches to dealing with this problem - sequence more genes (since each unlinked gene acts as a separate witness to the evolution of the group), sequence more samples (especially if doing so breaks up a long branch) or use a better model for the way mutations accrue in the genes you are studying. People have tried all three methods to get a better look at ratite evolution. Last year a group centred around the Field Museum in Chicago published a mutli-gene phylogeny of all birds that contained a big surprise for ratite evolution- the most recent common ancestor of all ratites flew.

As long as the ratites grouped together in a phylogeny it was reasonable to assume that they all inherited their flightlessness from the common ancestor of the group. The Field Museum study found that, in fact, the flying tinomous fit right in the middle of the flightless ratites. So, either the most recent common ancestor of the ratites and the tinamous flew and ratite lineages have subsequently lost that ability at least three times or that ancestor was grounded and the tinamous have rediscovered flight. In vertebrates the evolution of true flight has happened three times (in bats, pterosaurs and birds) while there are hundreds of examples of birds that have given up on flying. Moreover, a group of flying birds that are prone to flightlessness is hardly anything new - at least 30 species of rail (including our own weka and takahe) have taken to life on the ground. Given the ways the odds are stacked towards losing flight it seems probable the common ancestor that relates tinamous and ratites flew. The Field Museum study didn't include any moa species and didn't attempt any molecular dating so it's hard to see just how the ancestors of the kiwi and the moa made it to New Zealand

A new study (I knew I'd get to it eventually) published in Systematic Biology throws some light on the New Zealand ratite story. Matt Philips and a team of researchers from the Alan Wilson Centre at Massey University took another look at the mitochondrial dataset used in Cooper et al's 2001 study by adding more kiwi species and using models of DNA evolution that avoid some of the pitfalls of the ratite phylogeny's difficult shape. The new ratite tree and a molecular clock analysis based on that tree confirm the idea of multiple loses of flight in the ratites and add a new finding - the closest living relatives of our giant moa are the quail-like tinamous:

So what does the new understanding of ratite relationships mean for our ideas about the origins of New Zealand's ratites? The molecular clock doesn't quite tick with the regularity of a stopwatch, so there is a good deal more uncertainty in the timing of the events presented above than the precisely defined nodes suggest. Still, even with the uncertainty of molecular dating taken on board we can safely say that both the New Zealand ratite lineages departed from their closest relatives after the Tasman Sea opened up.

The revelation that the tinamous are the moa's closest living relatives suggests that the moa had ancestors that could fly. So, it seems the first proto-moa to arrive in New Zealand flew, or more likely was blown, here from Antarctica. Antarctica? It still seems amazing to me but 30 million years ago Antartica was still attached to South America and, without the circumpolar current to isolate from the world, was a relatively verdant continent. We know from fossils that Antarctica supported southern beech forests (still found in Chile, New Zealand and Australia) and marsupial mammals (strangely absent in New Zealand but still present in Australia and South America) so it's no great stretch to propose the representatives of another Gondwanan group lived there. Antarctica certainly seems like a more likely jumping off point for dispersing proto-moa than South America, but either way it certainly seems they made it here under their own power.

The mode of dispersal for the kiwi's ancestor is a little less clear. As we've seen we can be quite sure that they arrived in New Zealand after the Tasman Sea opened up and there is really no good evidence that there was ever a land-bridge across that sea. We can probably rule out walking. If we disregard the problem of dispersal for a second the simplest way to explain the distribution of flightlessness on the Phillips et al phylogeny is with a single loss of flight in an ancestor shared by kiwis and the Australian ratites. Under that scenario the kiwi would, presumably, have had to raft to New Zealand. Alternatively, given that we've seen the ratites seem to have an inbuilt propensity to becoming flightless we might imagine that the common ancestor shared by the kiwi and the Australian ratites could fly and each lineage has since lost that ability. In this case the kiwi could simply have flown from Australia to New Zealand (a journey that storms frequently inflict on Australian birds today). Without sufficiently old ratite fossils from either country it's hard to choose one scenario over the other.Long range dispersal by rafting is probably an important force in biogeography but if I was forced to make a bet I'd put my money on ancient flying kiwis.

The radical rethink of ratite evolution that a decade of molecular phylogenetics has forced on us raises a lot of interesting questions. What it is it about the ratite body plan, development or behaviour that makes them so prone to flightlessness? Is that repeated loss of flight, and consequent lack of pressure to keep their weight down, enough to explain the trend towards gigantism? The authors of the most recent paper suggest both trends might be explained by ratites on each continent filling the ecological niches left by the extinction of the dinosaurs. The dates on their tree are certainly consistent with the idea that each ratite lineage independently took to the ground 65 million years ago but without more fossils and more precise dates for each split it's very hard to test the idea further. I'm sure the story of ratite evolution has more surprises for us to uncover.

Outrageously geeky aside: these sorts of phylogenetic trees can even fall into the terrifying Felsenstein Zone in which the confidence with which you estimate the wrong tree increases as you throw more data at it.

---

Links to the primary literature are provided below but you should also check out Simon Collins excellent piece in the Herald and Mike Dickison, who got his PhD studying giant flightless birds and wrote about the idea that ratites flew to New Zealand way back in 2007.

Cooper A, Lalueza-Fox C, Anderson S, Rambaut A, Austin J, & Ward R (2001). Complete mitochondrial genome sequences of two extinct moas clarify ratite evolution. Nature, 409 (6821), 704-7 PMID: 11217857

Harshman, J., Braun, E., Braun, M., Huddleston, C., Bowie, R., Chojnowski, J., Hackett, S., Han, K., Kimball, R., Marks, B., Miglia, K., Moore, W., Reddy, S., Sheldon, F., Steadman, D., Steppan, S., Witt, C., & Yuri, T. (2008). Phylogenomic evidence for multiple losses of flight in ratite birds Proceedings of the National Academy of Sciences, 105 (36), 13462-13467 DOI: 10.1073/pnas.0803242105

Phillips, M., Gibb, G., Crimp, E., & Penny, D. (2009). Tinamous and Moa Flock Together: Mitochondrial Genome Sequence Analysis Reveals Independent Losses of Flight among Ratites Systematic Biology, 59 (1), 90-107 DOI: 10.1093/sysbio/syp079

Labels: biogeography, evolution, might interest someone, moa, new zealand, phylogenetics, ratites, sci-blogs, science