Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Nicky Bay is a superb photographer of small animals. I don’t think he’s technically a “reader” of this site, but I wanted to put his pictures under this category. Nicky has a Flickr site here, a Twitter page here, and a website, Macro Photography in Singapore, here. I’ve featured his photography three times on this website (here, here, and here).
He recently had a wonderful post called “5 Mysterious Structures From The World’s Smallest Architects,” but I’ll give the link below the fold. First I want you to guess what kind of creature made these structures. Nicky let me use the photos, which are copyrighted and cannot be reproduced without permission.
[JAC: Greg wrote about Darwin, oceanic islands, and the Falkland Islands fox about six years ago, and gives the link to that post below. But I thought I’d add the link here at the top as well, because it’s a very informative summary of how islands buttressed Darwin’s theory of evolution, as well a discussion about how a fox could have colonized the distant Falkland Islands.]
by Greg Mayer
Jerry’s back from his southern sojourn now, and may have made some posts from Chicago by the time you see this, but as he settles back in I thought it would be good to recall the lessons that another famous evolutionary biologist learned in the Falklands. Although we all associate Darwin with the Galapagos, his visit to the Falklands (also during the Beagle voyage) supplied an important bit of evidence in his thinking about islands, and the phenomena of island life were crucially important components in his argument for evolution.
Darwin was a bit perplexed by the Falklands. In many ways they seemed like oceanic islands—islands never connected to a continent, which had received their biota from across the seas by what Darwin called “occasional means of transport”. There was only a single native species of land mammal on the Falklands: the Falkland Islands fox, which was clearly related to South American foxes. (South America has a modest radiation of canids, which are variously called dogs, foxes, or wolves in English). The mammal fauna was thus depauperate (few species); disharmonious (lacking major ecological or taxonomic groups); and showed affinity to the fauna of the nearest continent (the effect of distance)—all of these are characteristics of oceanic islands.
Canis antarcticus, by George Waterhouse, from the Zoology of the Beagle. The increasing human population, and consequent increased disturbance and hunting, led to the extinction of the Falklands fox by the late 1800s.
How the fox got to the Falklands is an issue that concerned Darwin, but that’s not what I think was most important. (The issue of how they arrived, and when, was largely solved a few years ago, and we discussed it here at WEIT: the short answer is that lowered sea levels during the last glacial maximum greatly shortened the distance to the continent, and the fox came across, perhaps floating on ice floes, as Arctic foxes do.) The problems that the Falklands helped Darwin with most was why oceanic faunas were depauperate and disharmonious. Darwin’s evolutionary hypothesis was that it was difficulties of dispersal that led to oceanic faunas being apparently “undercreated”.
But there was an obvious alternative explanation: the ecological conditions on the islands are unsuitable for a species-rich, harmonious, fauna, despite seemingly appropriate physical environmental conditions. The oceanic faunas were not “undercreated”, but inhabited by the ecologically appropriate species.
These competing explanations are easily tested by introducing exotic species to the island, and seeing how they fare. If they become established, then the cause of their absence is a failure of dispersal, not a failure of environmental suitability. This is where the Falklands helped Darwin, I think. The Galapagos in the 1830s were still nearly pristine, but the Falklands showed him the fauna of an island with little direct habitat disturbance, and a small human population. But the people who had settled the Falklands brought their animals with them. At the time of his visit, Darwin recorded wild populations of cattle, horses, pigs, rabbits, rats, and mice, with cats, dogs and sheep coming later. The Falklands were thus quite capable of supporting a diverse and harmonious mammalian fauna; the mammals just needed help getting there!
So we can see that exotic mammals of all sorts do quite well in the Falklands, and that Darwin’s evolutionary hypothesis is thus supported. Although I’ve read up on the Falklands, Jerry’s visit there is the first by anyone I know, and he has provided firsthand reports on, and pictures of, the exotic mammals. So here again is a bovine, the Belted Galloway:
and a dog:Jerry tells me that sheep are “all over the place there!”, but, unfortunately, he didn’t get any pix of them. So here’s one that I found on the Internet, by Jeremy Richards, who has also sagely captioned it:
I’ve just finished making a BBC World Service radio programme about the first animals. Anyone, anywhere in the world, can listen to it (it’s only 28 minutes long!) – you just have to register with the BBC (free, rapid and cost- and spam-free). Click on the pic to go to the BBC website:
The programme deals with two different ways that researchers are studying this question – by looking at fossils, and at DNA. In both cases I interview researchers and – in the case of the Ediacara – get to handle some fossils. I also ate some 600 million year embryos at Bristol University (to see what they tasted like, obviously), but we didn’t include that in the programme. . .
The fossil data relate to what are called the Ediacaran biota – strange fossils from before the Cambrian, around 570 million years ago. The fossils are very hard to interpret – they don’t look like much alive today – but an amazing technique for analysing cholesterol molecules in the rock, so organic molecules preserved for all that time, has confirmed that Dickinsonia, the thing in the picture above, was an animal. Other techniques involve looking at large numbers of Ediacaran fossils and seeing how their distribution relates to those of modern animals. All the data suggest that some of the Ediacaran weirdos were indeed animals, although we cannot know if they are the ancestors of any animal alive today.
The DNA data focuses on a different question, which DNA can answer – which of the groups of animals alive today was the first to branch off the tree of life? Traditionally there has been a straightforward answer to this: sponges, which are nerveless and tissueless. But 10 years ago comparative genomic studies dropped a bombshell – they suggested that the first group to branch off were the ctenophores or comb jellies. This has caused a huge row because it would mean either that nerves evolved twice – once in the ctenophores, and once in our ancestors, after the nerveless sponges branched off – or that the huge sponge group somehow lost the genes for producing nerves.
Many biologists (myself included) don’t like either of these options, and prefer the sponges as the first model, but the data are persistent. Or are they? I spoke to experts on both sides of this argument, which has caused quite a hoo-haa in the zoological community for the past decade.
Anyway, go ahead and have a listen – download it and listen to it on public transport or while you are exercising. NB: I made the programme with ace producer Andrew Luck-Baker.
If you are a teacher, especially if you teach animal evolution, please get your students to listen to it.
Duck update: Honey was gone this morning, though she was here with James all day yesterday. At 7:30 a.m., James was again swimming disconsolately around the pond, and even attempting to quack, though not much of a noise came out. (Previously he’d just uttered low quack-y noises, but now he opened his bill wide and tried a real quack, with pretty dire results.) I’m convinced he was mourning Honey’s absence.
Then, at 10:30, Honey was back! Lord knows where she went; this is a real emotional roller coaster, but surely presages the Big Migration. At any rate, here’s James sitting on the “bathtub” this morning waiting for his mate. He’s standing on one leg and stretching a wing. I like this picture a lot. James is a good mate and I don’t think Honey can do better:
Let’s end the week with some humorous wildlife photos, in particular the finalists from the 2008 Comedy Wildlife Photography Awards. You can see all the photos here, but I’ll put up my favorite five six. Coincidentally, three of them involve bears.
Appropriately following upon Jerry’s monstrous, triffid-like seed pod, an attack by tiny monsters on an Australian teenager has been splashed across world media, including the BBC and the New York Times. The victim, Sam Kanizay was cooling off after a football match by wading in the sea near Melbourne. After a half hour in the water, he emerged bleeding profusely from the ankles, and the bleeding did not readily stop. He was taken to the hospital and should be just fine.
Sam Kanizay being treated in hospital. Photo by Jarrod Kanizay, via Australian Associated Press.
The interesting question from a biological point of view is “What did this to him?” We have a natural history whodunit, with two contenders, both crustaceans, and both quite small: isopods or amphipods. The BBC, citing Genefor Walker-Smith, said it was amphipods. The Times said the consensus was that it was isopods. Sam’s father Jarrod put some meat out in the water, and collected a host of critters, and posted a video of them to Youtube.
Most people in the north temperate zone are probably familiar with what we call in New York “cement bugs”, but are known by many other names: sow bugs, pill bugs, rollie pollies, etc. These are isopods, and there are marine ones called sea lice. Amphipods are less familiar in the Northern hemisphere, as they are aquatic and marine, and thus less commonly encountered. (There are terrestrial ones in the Gondwanan continents.) The ones that live at marine beaches are called sand fleas. One way to tell at least the usual ones apart is that isopods are dorso-ventrally compressed (‘squashed’ from above); while amphipods are laterally compressed (‘squashed’ from the side), and typically lay and move about lying on their sides. Both are said by the news reports to occasionally bite people.
In the video, you can clearly see that the critters are amphipods– pause the video, and enlarge on the screen if necessary, to see this. The Times quotes Alistair Poore, of the University of New South Wales, as also saying the critters are amphipods. However, although Jarrod trapped them by using meat as a bait, it’s not certain that what he trapped are the same things that bit Sam.
Here’s a tweet that Grania found. I’m pretty sure I know what this thing is (hint, it may not be an adult animal. . . ), but I’ll leave it to the readers to guess.
