Me Nature

In the Galapagos

I´ve got a couple of hours in Puerto Ayora (on Santa Cruz, in the Galapagos), so I thought I´d post a quick note.

I can recommend the Galapagos. For a start, the landscape is more varied and more beautiful than I expected; somehow in my head it was all rocks, but from island to island the colour of the rocks and soil changes, the vegetation varies – I mean it´s mainly pretty arid, and so it´s lots of cactus and thornbushes, but one island will be an expanse of rippled black lava with a few small cacti, and another will be densely covered with bushes. This afternoon we´re going to the highlands for the first time, where it´s actually quite green.

We´ve seen most of the Galapagos specialties now – the two iguanas, the flightless cormorants, the finches (5 of the 13 species so far). Wild giant tortoises this afternoon. I´ve snorkelled with sea-lions and penguins and turtles, I was particularly thrilled wih the penguins.

Actually though, apart from the special Galapagos stuff, it´s been nice just being at sea. I hadn´t really thought about it before I came, but it´s great just being able to watch shearwaters and storm-petrels from the boat. And we´ve had dolphins riding the bow-wave of the boat. But almost my most exciting marine sighting was watching manta rays jump clear of the water and tumble back with a big splash.

The famous tameness of the animals is quite interesting; I expected it of the endemic species that have evolved in an environment without predators, but species like Great Blue Heron, which are wary of people in the rest of the Americas, have been letting us get within about 10 feet. We watched one grab a newly hatched turtle from below the sand.

So it´s all good.

Culture Nature

Animals in Translation by Temple Grandin

Oliver Sacks fans will remember Temple Grandin as the autistic slaughterhouse designer in An Anthropologist on Mars. She has a particular affinity with animals and has used her talent for understanding them to help her design corrals, feedlots and slaughterhouses which are less stressful for the animals.

The subtitle of Animals in Translation is ‘Using the Mysteries of Autism to Decode Animal Behavior’. Grandin uses her insights as an autistic person to help explain how animals behave and in the process explores the nature of autism itself. That means the book is operating at the intersection of a whole range of different subjects — evolution, selective breeding, autism, animal behaviour, slaughterhouse design, stock handling, animal training — which all shed interesting light on each other. I didn’t come out of it thinking “Ah, now my perception of animals has been transformed!” but I did find it was full of interesting insights. For example, she says that it’s difficult to tell how much pain or distress is being suffered by prey animals (cows, sheep, goats); they try to disguise it, since a sickly animal is likely to be a target for a passing wolf. Predator animals, on the other hand, have no such tendency and will, if anything, exaggerate their pain. As you’ll know if you’ve ever stepped on a cat’s paw.

It’s good. One of those books where you keep reading bits out to people. And if you haven’t read any Oliver Sacks you should read those too.


Flies, flies and more flies.

Someone posted this photo of a scorpionfly to the Flickr group ID Please:

Schorpioenvlieg, originally uploaded by Wue.

Which reminded me of something I said a week or so ago.

I take a casual interest in insects and other invertebrates, but one thing you quickly realise is that they’re really hard. I first really appreciated this when, quite pleased with myself for recognising something as a ’scorpionfly’, I tried to look it up in a book and discovered there are something like 28 species just of scorpionflies in the UK.

Well, it turns out I was misleading you. There are only four species of scorpionfly in the UK. There are however 51 species of mayfly, 33 species of stonefly, and 189 species of caddisfly. And 158 species of thrip, 627 lice, 1709 bugs, 2400 species of butterfly or moth, 3900 beetles and 6900 true flies. Notice the numbers start getting suspiciously round for the bigger groups.

What I find staggering about these numbers (from Buglife) is that it implies there are so many different evolutionary niches available for such apparently similar creatures. Even the 51 species of mayfly are slightly mind-boggling, but how can there possibly be 6900 different ways of successfully being a fly?

I guess a lot of insects are specialised to a particular food source – for example most caterpillars only eat specific food plants and parasites usually have specific hosts, whether animal or plant. So that means every plant or animal species is in turn a potential opportunity for yet another species of insect.

I wonder how useful the lanaguge of ‘niches’ is anyway. It rather implies that each niche can only hold one species, that if two species are in direct competition for the same resources, one of them must inevitably lose out. I don’t know if that’s necessarily true; for example, if two geographically separated populations of a species evolved to look different, so that they would no longer interbreed, but kept living in essentially the same way (filling the same niche), and then the two populations mixed again, would one inevitably out-compete the other, or might they just live alongside one another?

Perhaps usually, the niches wouldn’t be quite identical anyway, and would just be heavily overlapping – the two species would be competing for some things but not others. Does that make a difference? Does it make it more likely that they would achieve a stable mixed population? I don’t know.

I assume evolutionary theorists have thought about these issues; I don’t know what conclusions they’ve reached.


After 200 million years of abstinence…

An interesting story about darwinulids. As far as anyone could tell, darwinulids (a type of crustacean) had been reproducing exclusively asexually for 200,000,000 years, but now a researcher has found 3 male specimens, which implies that at least one darwinulid species has sex.

Sex is a bit mysterious in evolutionary terms because it’s so much more efficient to reproduce asexually. Quite apart from the time-consuming business of finding a mate, sexual reproduction needs twice as many adults to produce the same number of offspring, and when you do breed, only half your own genes end up in the child anyway. That’s a huge reproductive disadvantage; yet pretty much all animals have sex. So it must offer some kind of dramatic short-term advantage to compensate for that reduced breeding rate. Even animals like aphids, which mainly breed asexually (aphids are born pregnant!) occasionally produce a few males and breed sexually as well.

The most popular theory is apparently that it helps fight disease and parasites – read The Red Queen by Matt Ridley for the details – but certainly its omnipresence implies that sex serves some kind of vital role. Which makes it hard to explain the few groups of animals that seem to have been merrily getting along without for tens of millions of years. If it is confirmed that darwinulids have been secretly shagging away somewhere all along, it removes an anomaly. That still leaves the marvellously named bdelloid rotifers, who have apparently been holding out for 40,000,000 years.

Nature Other

Atheism again

I said a few posts ago, about my own atheism, “I don’t believe in unicorns either, but I’m not about to go to any meetings about it.” Well, I haven’t been going to any atheist meetings, but I have been reading the comment threads at Pharyngula, which is a pretty good internet equivalent.

My own stance on evolution and religion is hard-line: I think the evidence for evolution is overwhelming, that anyone who doesn’t accept it is just plain wrong, and that standard compromise of evolution being somehow guided by God is just a muddle-headed cop-out. I get as angry as the next atheist at attempts to get creationism/ID taught in biology lessons. And as a social liberal, I don’t have much time for Christian fundamentalism in any circumstance, and I’ve done my fair share of internet Christian-baiting.

And yet, despite my own intellectual intolerance and the fact I share all the biases of the commenters at Pharyngula, I still find the atmosphere there toxic. There’s so much energy being expended on hostility and derision, such a sense of superiority on display. Anyone who rejects evolution – or believes in God, really – must obviously be an idiot or a liar. There’s not even an attempt to empathise with anyone who values faith over reason.

I don’t know. Maybe I’m getting soft. Or maybe I just recognise my own worse qualities in the people there. I should probably say, to be fair, that not everyone there matches the description I’ve just given. Perhaps no-one does, really; but that’s the overall tone of the site. And I should also point out the endless provocation from the anti-evolution people. But still. I’m tempted to say that I think it’s bad strategy, that they’re alienating more people than they’re persuading, but I have no idea. What I do think is that, for want of a less spiritually loaded term, it’s just bad karma.


Transitional species

I was looking back at old PFFA threads yesterday, and there was an argument about religion, evolution and so on during which someone asserted that “there are no verifiable fossil records of transitions from one species to another.” This morning I feel inclined to make a point which I don’t think is always appreciated by people who have never had to deal with issues of taxonomy; which is that, quite apart from the fossil record, transitional species are all around us.

I should probably start by establishing what a species is. A canonical species is a population of animals that can interbreed freely with each other and only with each other. In evolutionary terms, one species becomes two at the moment when the populations diverge so much that the split becomes irreversible. Because evolution works by a process of gradual changes, there will always be an ambiguous period when it is unclear whether that split has occured.

The obvious mechanism for a split happening is that two geographically separate populations develop in different directions. On the local level, the vast majority of species are easily separable from each other, but on the broader view, ambiguities about species status are almost the norm.

Let’s talk about wrens. To Europeans, ‘the’ wren is a familiar bird; tiny, loud-voiced, with a place in folklore and poetry. Most don’t realise that wrens are actually a New World family. All over the Americas there are dozens of species of wren, including some really quite large species:

Cactus Wren, originally uploaded by Bournemouth Pilot.

But at some point, one species, Troglodytes troglodytes, made it across the Atlantic or the Baring Straits and spread all across Eurasia. The particular species is still found in North America, where it’s known as the Winter Wren. It probably came across fairly recently, in biological terms, because it’s still similar enough across its range to be classified as a single species, and there are very very few species of small, non-migratory birds which are native to both North America and Eurasia. Nonetheless, there’s enough local variation – in colour, size, proportion – that it is classified into no fewer than 46 sub-species. These are two of them; the first was taken in mainland Scotland so is presumably Troglodytes troglodytes indigenus:

This is T. t. zetlandicus taken in the Shetland Islands (i.e. about 100 miles north of Scotland):

zetlandicus is slightly larger, slightly darker and greyer, and has a slightly longer tail. The differences are small, but consistent. In the opinion of the taxonomists, none of the 46 subspecies of Winter Wren are so distinct as to represent a permanent split. I suppose the implication is that, if a few Shetland wrens were taken to the mainland, they would be absorbed into the local population. But given a few thousand years more, perhaps they will be so distinct that they will need full species status. Or perhaps that population will die out, from disease or freak weather. Or perhaps wrens from the mainland make it across the water just about often enough to keep the gene pool from diverging completely.

This is what a transitional species looks like. Boring, isn’t it? Not a monkey-man or a walking fish, just a rather drab bird which is a bit larger and a bit drabber than its closest relatives. That’s what evolution at the dirty end is like – grindingly slow and mundane.

One more example. The first is a Great Blue Heron, Ardea herodias, from North America, the second is a Grey Heron, Ardea cinerea, found across Eurasia.

Looking at them, there’s no doubt at all that they are descended from the same species. Some time a few thousand years ago, or a few tens of thousands of years ago, enough herons crossed the ocean in one or other direction to establish a breeding population. It was recent enough that the two species look extremely similar, but they are distinguishable; the Great Blue has a darker neck and red on the thighs and underwing coverts, and in breeding plumage has more plumes on the neck.

The world is full of pairs of species that are so similar that they obviously split from the same species fairly recently, and subspecies that are recognisably different from each other. Taxonomists change their mind about classification all the time as research continues, splitting species up or lumping them together. For example, when I first saw Hoopoe in Africa about 15 years ago, my bird book said it was the same species as the Hoopoes in Europe. But according to Avibase, different taxonomists split Hoopoe into different combinations of four different species: Eurasian Hoopoe, Central African Hoopoe, African Hoopoe and Madagascar Hoopoe. For example, the fourth edition of Clements recognised two species, African and European; the fifth edition demoted African Hoopoe to a subspecies but promoted Madagascan Hoopoe to a full species.

Taxonomy is an important and useful exercise in establishing the relationships between animals, but the neatness of the categories can be misleading. The whole scheme of putting animals into a sequence of different boxes makes it look like you’re establishing fundamental patterns in the organisation of life:

Shetland Island Wren

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Troglodytidae
Genus: Troglodytes
Species: T. troglodytes
Subspecies: T. t. zetlandicus

But most of the categories have no special status. The species is the closest thing to a well-defined unit that has some kind of observable reality, and even species, as I hope I’ve indicated, are a lot less clear-cut than you might imagine. All the others are just approximate indications of relatedness. Two species in the same genus are very similar and therefore closely related; if they’re only in the same family, they’re a bit less closely related, and so on.

That’s not to say that the individual categories – the order Passeriformes, for example – are imprecise or misleading; but the term ‘order’ has no definable meaning, beyond “a rank between class and family”. If taxonomists feel the need to make finer distinctions, they just add in new ranks, like a superorder or a suborder. Don’t let the neatness of the taxonomical hierarchy fool you into thinking that the tree of life is correspondingly neat.

[All photographs © their respective photographers]