Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Thursday, June 30, 2005

Females are from Venus, males are from... males?

There is a really cool paper just published in Science (links at end).

It transpires there is a fire ant, endemic to French Guiana and New Caledonia (that's a wide distribution - have French colonials carried them from one place to the other? - ah, yes, the paper says so), called Wasmannia auropunctata, which has an odd sexual reproductive system.

Now we are used to ants and other colonial insects having various kinds of haplodiploidy and what have you, but this one is really wacko. Rather than males having a haploid complement of genes or anything, females and males are clones of each other. That's right - the male and female genetic pools are entirely distinct. The females just clone themselves, and the males replace all the female genetic material and essentially parasitise the females as reproductive incubators of their own genes.

This is cool for several reasons - one is that it shows that the haplodiploid system of other ants allows some seriously strange outcomes to evolve - apparently once you have that, this is now evolvable (You Can Get There From Here). The other is that is massively screws the biological species concept. And that is always a good thing.

According to the BSC, a species is a reproductively isolated sexual group. Here is a group. It is reproductively isolated from other ant species. It is also sexual (males need females). But there is no mixing of genetic material (or so the paper says - one wonders if there isn't a little cross contamination). Worker ants, who are sterile, are produced by normal sexual reproduction, though.

Now typically, one explanation of sexual reproduction is that it enables a species to "outrace" parasites and pathogens by making genetic variability too complex for the pathogen/parasite to target. I wonder what happens here?

On the other hand, a longstanding problem with sexual reproduction is that, by definition, it halves the reproductive fitness of both sexes, since only half their genetic complement gets passed on in each progeny. These guys have overcome that.

Gotta love nature - it'll screw with any generalisations you care to make in the end.

Sidenote: I suspect the person for whom the genus Wasmannia is named is Freiderich Wassman, a German entomologist at the turn of the 20thC. Funnily, Wasmann, a strong Catholic, opposed evolution in

Wasmann, E. (1910). Modern Biology and the Theory of Evolution. London, Kegan Paul, Trench, Trübner.

Late note: David Quammen has a good explanation and figure of the process here in Nature.

See Report

See Paper