Posts Tagged might interest someone

Lawrence Krauss on a bad day David Winter Mar 17

1 Comment

Dunedin got to see Lawrence Krauss on a good day and a bad day this week, but that’s not to say one of his presentations was better than the other. Yesterday the award winning physicist and scientific communicator revealed to his audience that his outlook on life changes from day to day. On good days he can revel in the wonder of a universe that could come to know itself due to a series of accidents that started 10-31 seconds after the big bang and allowed the creation of first matter then atoms, stars and planets and finally astronomers. On bad days he despairs at the lack of scientific thinking in journalism and politics and thinks these problems, and the anti-scientific forces that fuel them, will probably prevent us from doing anything meaningful about climate change.

Krauss’ awe inspiring story of an atom’s journey from the birth of the universe to its death will gain nothing from my retelling it. If you weren’t able to see it then you’l be glad to know his talk was a précis of his excellent book ATOM: An Odyssey from the Big Bang to Life on Earth…and Beyond and covers similar ground to this recored lecture. Perhaps I’m a masochist and a pessimist, but I’m going to skip the awe inspiring story to focus on what Lawrence Krauss thinks about on a bad day. His talk on “Science, Non-Science and Nonsense” described the sources of scientific confusion in society and the tactics used by those groups that seek to take advantage of it.

Krauss argued that the goal of science education and science communication should be to make sure everyone develops a functioning bullshit filter. He didn’t express his thesis quite as bluntly as that, but his core idea is that spreading a scientific mindset would allow us to short circuit needless debates (is global warming real?) and let us get on to the important ones (what are we going to do about it?). He used a neat example to illustrate how this sort of scientific common sense could stop nutty ideas before they get started. UFO enthusiasts often cite the ability of the lights they observe to perform right angle turns at speed as evidence of their otherworldliness. In fact, Krauss pointed out, common sense should tell us that these apparently amazing maneuvers are evidence that the lights in question are not being emitted by a massive object moving through the sky. The only way to turn at a right angle is to stop then change direction, for a UFO to do all its slowing down and stopping so quickly a human observer couldn’t perceive it would generate G-forces with a strength about 2000 times greater than earth’s gravity. And quite a mess.

If the evidence used by UFO junkies is so silly then why do continue prosper? Why aren’t people already filtering this sort of nonsense? The standard of scientific reporting in the media certainly has a lot to answer for. Krauss cited the normal concerns, a fractionated media market means viewers can choose a source of news that confirms their biases and the innate need of journalists to present balance is misplaced in science stories when, in almost every case, one side is wrong and we usually know which side that is. He also mentioned something I hadn’t thought about before. According to Krauss, part of the problem with science coverage in mainstream reporting is that journalists don’t feel qualified to make scientific pronouncements. Writers and broadcasters are happy to make bold statements on politics, financial markets and sports but will shy away from even a scientifically uncontroversial statement like “evolution is a fact.”

Scientific understanding might not be helped by meek journalists and the false equality of balance but most journalists aren’t setting out to deliberately mislead the public on science. Unfortunately, there are forces at work that are doing just that. Krauss had a tonne of examples from the culture wars in his native USA to draw on but he also took the time reminded us of our home grown cranks, citing the New Zealand Climate “Science” Coalition and Ray Comfort (The Apologist’s Nightmare ) as evidence we aren’t immune to anti-science in New Zealand. As you’d expect Krauss exposed just how vacuous the claims of intelligent design creationism and the objections of climate change denialists are, but he also attempted to deconstruct the PR strategies each group use. Both campaigns seek to take advantage of the public’s sense of fairness and journalists’ willingness to provide balance to any point of view. The Discovery Institute would have you believe their goal is simply to get their science a fair hearing in the classroom. But they don’t have a science. For normal science, theories only make it into the school curriculum after they’ve been proposed, tested, retested and confirmed. The ID crowd don’t want fair treatment, they want special treatment, to avoid that boring scientific process and start in the classroom!

Krauss could hardly have known this, but our own climate cranks play the same game. I hate to make an example of this article because the author usually covers science well, nevertheless it highlights the point. In an effort to provide balance to a story on how the IPCC might be made better the author contacted Vincent Gray for comment, here’s the paragraph

Wellington scientist and climate change sceptic Vincent Gray said the researchers were continually coming up with “new models” but they were still “fiddling the figures” and were unlikely to restore public confidence in their work until their projections were proven

That sounds pretty fair doesn’t it? Climate scientists can run their model forward in time and if their projections match observations we’ll take action. Actually, it’s absurd. As Krauss emphasised in his talk, the evidence for climate change doesn’t only come from models, we have tonnes of data that tell us the earth is warming and the seas are rising. Combine those data with the fact recent temperature records are within the uncertainties of the IPCC’s projections and sea levels are near to the upper bound of those projections and Gray’s sound bite seem less fair.

Krauss had more problems than solutions in his hour long presentation. In fact, it’s a testament to the passion he has for his science and skill he has as a scientific communicator that he managed make a talk made almost entirely of depressing facts seem invigorating. The only ray of hope Krauss offered us was that when people’s backs are to the wall they abandon their their preconceptions and to turn to science. In 2003 George W. Bush said that he believed “both sides” of the “evolution debate” should be taught in schools. In 2005 Bush was faced with the prospect of Avian flu becoming able infect humans. Confronted with threat of a flu pandemic the Bush administration dispensed with its evolutionary agnosticism and planned for the possibility of genetic mutations allowing viruses to pass from human to human. That sort of infectivity requires conformational changes in surface proteins which create a new function, exactly the sort of phenomenon the ID crowd think is so improbable as to be effectively impossible.

Krauss will be presenting something very similar to his Dunedin talk in Auckland next week. I’d encourage anyone who has the chance to get out and seem him, he’s a very chrasmatic and interesting speaker. You might even ask the question I really wish I did now- how are we going to fix all these problems?

Sunday Spinelessness – Extreme Close-up David Winter Mar 14

No Comments

Almost all the photos I’ve used to illustrate these Sunday Spinelessness posts have been taken with my fixed lens digital camera. I think it does a pretty nice job in macro mode but sometimes you just want to get a little closer to your subject. I photographed each of the landsnails I collected for my PhD research so that I could have a record of their pigmentation, which degrades once you preserve a specimen in ethanol. Obviously, the more detail I could get the better so I borrowed some very exciting toys from the department’s photography office:

macro

The camera is a DSLR with a 100mm f2.8 macro lens, an extension tube and a twin flash. The mammal crashing this invertebrate-celebrating series is me.

Of course, I couldn’t have a toy like this to play with and limit myself entirely to photographing snails. In amongst those important snail photos I have jumping spiders, hornets, geckos and really anything else that chanced across the porch I was taking photos on. One of the more striking subjects is this red-eyed fly:

ff2

And the head-on shot…

ff1

It turns out the pretty red-eyed fly is Oxysarcodexia taitensis, one of the Sarcophagidae. That family name gives you a clue to how this fly makes its living, it translates as “flesh eating” (it stems from the same root words as sarcophagus, the Greeks believed limestone ate away at corpses sealed in it). Most of the flesh-flies feed on dead animals but a few have earned a place in vertebrate nightmares, horror movies and even medical practice by depositing their maggots in on open wounds.

Relying on dead animals for food is a chancy business. Corpses are usually patchily distributed and there a plenty of other scavangers out there to compete with. This problem is especially bad for the larval stages of insects, without wings to get them to the next corpse their entire future depends on the continued existence of the flesh they are born on. The sarcophogids have developed a neat trick for making the most of corpse when they find one – they give birth to live maggots. Technically, the flesh flies are ovo-larviparous, meaning the larva develops inside an egg which is retained in the female until the larva hatches. Flesh-fly maggots can start eating as soon as they are born, maximizing their chances of getting through their lifecycle before another scavenger eats the corpse they live in.

It’s easy to get freaked out about a creature that spends it’s life eating decaying flesh but we should remember that flesh-flies play an important role in ecosystems. Sarcophigids and other scavengers turn dead flesh into living flesh. WD Hamilton, one of evolutionary biology’s most insightful and original thinkers, recognised the important role of carrion feeding insects in his burial instructions:

“I will leave a sum in my last will for my body to be carried to Brazil and to these forests. It will be laid out in a manner secure against the possums and the vultures just as we make our chickens secure; and this great Coprophanaeus beetle will bury me. They will enter, will bury, will live on my flesh; and in the shape of their children and mine, I will escape death. No worm for me nor sordid fly, I will buzz in the dusk like a huge bumble bee. I will be many, buzz even as a swarm of motorbikes, be borne, body by flying body out into the Brazilian wilderness beneath the stars, lofted under those beautiful and un-fused elytra which we will all hold over our backs. So finally I too will shine like a violet ground beetle under a stone.”.

Sunday Spinelessness – Survivor David Winter Mar 07

12 Comments

Until today these Sunday Spinelessness posts have been severely unrepresentative. I’ve talked about molluscs and myriopods and shown you photos of anthozoans and arachinids but nowhere in these posts have I included a post about a beetle. Which is a shame because, to a first approximation, every species on earth is a beetle. Really. Most animals are arthropods, most arthropods are insects and most insects are beetles. In all, 350 000 species have been described so far, about a third of the total number of species from all groups. The star of today’s piece is one of New Zealand’s 4 500 described species.

longhorn0

I found our star stuck in one of those deadly rhododendron shoots . I guess if I was a cold-hearted documentarian, interested only in recording the happenings of the natural world, I would have left him there to struggle. But, really, I’m just a sucker for handsomely striped elytron so I helped disentangle him from the sticky shoot.

longhorn1

Those impressive antennae place our specimen in the order Cerambycidae, the long horn beetles, which includes the famous huhu beetle. I can’t identify it down to species but it’s likely in the genus Coptomma (for what it’s worth, the taxonomic shorthand for ’some species in Coptomma’ is ‘Comptomma. sp’). Our Coptomma didn’t seem to have any long lasting effects from his run in with the rhododendron’s sticky trap, he wandered off my life-raft leaf and set about cleaning himself up:

longhorn2

You have to be in to win… David Winter Feb 26

1 Comment

Research Blogging Awards 2010 FinalistSo, in a fit of egotism and optimism I nominated myself (and a bunch of other people) for the Research Blogging Awards – putting myself forward in the category of “Best Lay-Level Blog”. The finalists were announced today and it seems I made the list. Apparently in the next stage researchblogging.org members vote for their favourite blogs in each catergory. I think it’s safe to say I’ll be out of the running once voting starts but I’m really quite chuffed and… damn it I’m just gonna say it… it’s an honour just to be nominated among real writers lie Brian Switek of Laelaps and Ed Yong of Not Exactly Rocket Science and the bloggers behind The Lay Scientist, Observations of a Nerd, Mauka to Makai and Cancer Research UK’s blog.

Congratulations to all the finalists but in particular to Aimee Whitcroft who does a lot of work behind the scenes at sciblogs and has been nominated in the chemistry physics and astronomy category.

Sunday Spinelessness – Animals that don’t move David Winter Feb 20

No Comments

There aren’t many universal laws in biology. Snails proved Dollo wrong, retorviruses did for Crick’s Central Dogma of Molecular Biology and every lesson on Mendel’s Laws of Inheritance includes a section of the exceptions to those rules. Biology’s disregard of human laws notwithstanding, you might think, at least as far as macro-organisms are concerned, you could safely generalise that animals move and plants stay still. But once you consider the ocean even that generalisation can’t be supported; corals, bryozoans, sea squirts, anemones and sponges are all animals that spend their adult life in one spot.

While I was in Masterton for christmas my girlfriend went to Vanuatu (no, you’re right, that doesn’t quite seem fair…) with a waterproof camera so I’ve stolen a few of her photos of coral to illustrate todays sunday spinelessness.

P1000095

coral2

It’s easy to see why early naturalist thought corals were plants but what you are looking at in those photos is not a single organism, rather it’s a colony of tiny genetically identical animals. Corals are members of the phylum Cnidaria (the ‘c’ is silent) which includes corals, anemones and a diverse bunch of animals we call jellyfish. Such a diverse collection of animals are united under the name Cnidaria because they all employ the impressive nematocyst, a barbed harpoon like cell, to catch and deliver toxin to their prey. Cnidarians have two distinct life stages – a swimming “medusa” (adult jellyfish being the classic example) and a sessile polyp (like the sea anemones familiar to rock pool fossickers the world over). Individual coral colonies (termed “heads”) are made entirely of polyps which reproduce asexually depositing a calcium carbonate base as they grow – the exact pattern in which polyps bud from their parents determines the shape a coral head takes.

Many tropical corals supplement their diets by forging a symbiotic relationship with swimming algae (arguably plants that move…) called zooxanthella, the algae get carbon dioxide from the coral’s respiration while the coral gets energy from the algae. This relationship is of huge importance in the tropics because it allows corals to grow in those region’s warm, nutrient poor waters. Without coral reefs, made from thousands of years of calcification from corals, tropical waters would be nowhere near as biodiverse as they are now and people whose love of animals only goes as far as that peculiar phylum Chordata should care about that:

c5

c4

As always, you can click on any of those photos to see higher-resolution versions.

Sunday Spinelessness – robber fly David Winter Feb 14

No Comments
robber fly eating a blowfly

I’ve said before that the bugs in my parents’ back yard seemed especially hungry over the Christmas break. Above you see more evidence to this fact. In the lower half of the photo is a robber fly and above is its meal, a blowfly of some sort. I’ve never seen live robber flies in Dunedin (though there is a dead one here) but the species captured above seems to be reasonably common in the Wairarapa. The first time I spotted one of them I struggled as to where to place it among the insects. The robber flies have long slender bodies and large rounded eyes which misled me into thinking that first sighting might be a small dragonfly. The real taxonomic position of the robber flies is spelt out in bright yellow in the next photo.

robber fly - check out the halteres

That bright yellow structur under the main wing is a haltere. Most insects have two sets of wings and we can tell quite a lot about where a given species fits in the insect scheme based on how it uses those two. Dragonflies and damselflies use both for flying, in beetles the forewings are “sclerotised” into a rigid case that protects the flight wings and the “true flies” ( order Diptera) have turned thier hind-wings into halteres – greatly reduced wings which act as gyroscopes stabilising the flies’ flight and allowing them to perform aerobatic tricks. The robber flies from the extremely widespread and speciose family dipteran family Asilidae which includes a staggering 7 000 described species, meaning there are rather more robber fly species in the world than there are mammalian ones.

The features that led me to mistake that first robber fly that I saw for a dragonfly are likely the result of convergent evolution – dragonflies and robber flies are both predators that specialize in taking other insects on the wing. The robber flies differ from odonates in having piercing mouth-parts which they use to inject first a neurotoxin then digestive enzymes into their prey. The blowfly in the photos in this post is paralysed and its tissues are in the process of being liquified and sucked through the robber flies mouth parts. But ever before the neurotoxin entered the blowfly’s body it was done for, the robber fly’s strong “raptorial” legs are covered in sharp spikes and end in claws that offer little hope for escape once a catch is made.

robber1

Charles Darwin and the Origin of Spouses David Winter Feb 12

2 Comments

Happy Darwin Day everyone! Today would have been Charles Darwin’s 201st birthday so around the world geeks are celebrating, churches are standing up to creationism and at least a few biologists are trying to eat their way through the tree of life. With Darwin Day falling so close to Valentines Day I thought it might be fun to forget about Darwin’s science just for a few minutes and look at his attitude to love and marriage.

No one has ever accused Darwin about making a rush to judgement about any topic. Just as he spent years poring over the minutest detail of barnacle anatomy before he published The Origin he gave the topic of marriage careful consideration before singing on. In fact, preserved in his notebooks we have a record of the deliberations he undertook. Sometime in 1838 Darwin turned to a new page in his notes and drew a line down the middle, he added the headings “Marry” and “Not Marry” to either side of the line an proceeded to list the pros and cons of either decision. You can see the notebook here but below (presented without comment) is a transcript :

Marry

  • Children — (if it Please God)
  • Constant companion, (& friend in old age) who will feel interested in one
  • Object to be beloved & played with —better than a dog anyhow.
  • Home, & someone to take care of house
  • Charms of music & female chit-chat.
  • These things good for one’s health.
  • Forced to visit & receive relations but terrible loss of time.

Not Marry

  • No children, (no second life), no one to care for one in old age.
  • What is the use of working ‘in’ without sympathy from near & dear friends—who are near & dear friends to the old, except relatives
  • Freedom to go where one liked — choice of Society & little of it.
  • Conversation of clever men at clubs
  • Not forced to visit relatives, & to bend in every trifle.
  • To have the expense & anxiety of children
  • Perhaps quarelling
  • Loss of time.
  • Cannot read in the Evenings
  • Fatness & idleness
  • Anxiety & responsibility
  • Less money for books &c
  • If many children forced to gain one’s bread. (But then it is very bad for ones health to work too much)
  • Perhaps my wife wont like London; then the sentence is banishment & degradation into indolent, idle fool

On the “marry” side of the page Darwin makes his conclusion:

  • My God, it is intolerable to think of spending ones whole life, like a neuter bee, working, working, & nothing after all.
  • No, no won’t do. — Imagine living all one’s day solitarily in smoky dirty London House.
  • Only picture to yourself a nice soft wife on a sofa with good fire, & books & music perhaps — Compare this vision with the dingy reality of Grt. Marlbro’ St.
Darwin made his list a year before his engagement to his cousin Emma Wedgwood and it seems from their letters to each other and their personal diaries that Charles’ “nice soft wife” more than made up for the money he didn’t get to spend on books. There is a movie out at the moment which apparently makes much of the religious divide between the Darwins. Emma was certainly a devout Unitarian (apparently she made the children turn their heads during the Nicene Creed and their local Anglican church!) who worried that Charles’ skepticism of religion would prevent them from being joined in Heaven. Religion was a sticking point for the Darwins but they reached a sort of detente on the topic epitomised by one of Emma’s letters to Charles during their engagement:

When I am with you I think all melancholy thoughts keep out of my head but since you are gone some sad ones have forced themselves in, of fear that our opinions on the most important subject should differ widely. My reason tells me that honest & conscientious doubts cannot be a sin, but I feel it would be a painful void between us. I thank you from my heart for your openness with me & I should dread the feeling that you were concealing your opinions from the fear of giving me pain.

Sunday Spinelessness – now with 150% more links David Winter Feb 07

2 Comments

None of my photos today, instead I thought we should have a look at what some of web’s other inveterate invertebrate bloggers have been up to.

Giant Microbe’s plush Tardigrade


Weird Bug Lady’s plush planarians

Did the Moa’s ancestor fly to New Zealand? David Winter Feb 04

24 Comments

ResearchBlogging.org

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

Sunday Spinelessness – Motherly Devotion David Winter Jan 31

No Comments

I promised last week that I’d come up with something a bit more cheery than photos of dead flies for the next Sunday Spinelessness post and what could be more uplifting than portraits of motherly devotion? Of course, in this case the mother is a spider. The New Zealand lynx spider Oxyopes gracilipes.

Gravid Lynx Spider

Lynx spiders are a family (Oxopidae) of very active and fast running hunting spiders. The swollen abdomen of the female photographed above is evidence of her gravidity (I was tempted to dedicate this post to Harvest Bird who finds herself in the same condition but I’m not quite sure how someone a little less arachnophilic than I would take that). A few days before I spotted the gravid female I’d taken some pretty poor photos of a male lynx spider on the same plant so we can probably assume he’s the father.

LynxM

And because that photo really is pretty awful here’s another male lynx spider I found crawling around on our house

lyncM2

That’s a bit more like it. In this one you can see a few of the defining morphological characteristics of the lynx spiders – spiny legs, a hexagonal arrangement of eyes very large and palps in males. O. gracilipes also displays a few behavioral traits that are typical of lynx spiders, it’s active during the day there is a great deal of maternal investment in offspring. Here’s our female again, a little over a week after the first photo.

lynxF2

She’s lost her former globose shape because she’s laid her eggs. The silk she’s spun around the leave is protective egg sag but lynx spiders take protection very seriously – they won’t leave the fate of their eggs to a bit of silk and chance. I checked on the egg sac almost every day for two weeks and never found the lynx spider more than a few centimeters away. Little is known about the behaviour of our lynx spider but their American counterparts have been known to relocate egg sacs when they are threatened by predators or starve to death while standing guard. In the end I had to leave before the spiderlings hatched but in Spiders of New Zealand and their Worldwide Kin Ray and Lyn Forster tell us that the female wanders off shortly before that event.

As ever you can click on the images to get to a higher resolution version.

lynxF3