Sunday, June 14, 2009

Evolution2009: Sunday

Today was more interesting for me after attending a few talks of direct relevance to our ongoing work at CORE. I began my day with the winners of the ASN young investigators award. I'm just going to record a few impressions rather than give exhaustive summaries

First was a talk by Luke Harmon of the University of Idaho on adaptive radiation. He opened by discussing the problem of defining an adaptive radiation, taking the pragmatic (but admittedly unsatisfying) tactic of "I know it when I see it." He also cited Dolph Schluter's definition, "evolution of ecological disparity within a rapidly multiplying lineage." That seems unsatisfactory, since it is more of a description of the origin of radiations than an actual definition, by which you could recognize a radiation in the present. Nevertheless, he's been using a method to identify statistically significant differences in taxon birth/death rates in different parts of the gnathostome tree, which should identify groups that are evolving unusually rapidly or slowly. Those that are more rapidly evolving would be radiations, and slower groups are "living fossils." It worked pretty well, I thought, but I definitely think there needs to be fossil taxa included. It identified such groups as the coelacanths and tuataras as living fossils and pecomorph fish and neoaves birds as radiations. He mentioned that there was no reasonable model to explain living fossils, but frankly there's not one in creationism either. Why do some groups explosively radiate after the Flood and others do not?

The next presenter was Jason Kolbe from UC Berkeley speaking on invasive species. He also opened with a great question that I've been wondering about for some time: If genetic bottlenecks are so harmful, how can invasive species be so successful? The basic answer he's finding is that the admixture of haplotypes after multiple introductions provides the genetic variation that makes a successful invasive. He's also got some really killer experimental work on natural selection in introduced anoles in the Caribbean.

What I wondered after these two talks was whether anyone's trying to put these two topics together? Island radiations must have all begun as invasive species, right? Or just exotics? I'm sure someone must be thinking about this. I'm definitely going to have a conversation with my colleagues when I get back to CORE. (You have been warned.)

Then I went to the wrong session (apparently there's two engineering buildings on campus), so I didn't get to find out why all chilies aren't hot. My students will be disappointed. I did get to hear about one of the few endemic land vertebrates on Bermuda. It's a lizard called Plestiodon longirostris which phylogenetically appears to be a basal lineage of the North American Plestiodon group. That's unexpected since it's way out on Bermuda, and the nearest species geographically are not the nearest species phylogenetically. Based on all we know about island biogeography, island endemics on oceanic islands are most closely related to the species on the nearest mainland. Not this time. It is definitely an interesting puzzle. Kind of a sad story, though, since the lizard is critically endangered from all the human development on Bermuda.

After lunch, I learned about the freaky Heterorhabditis worm and its bioluminescent symbiont Photorhabdus. Seems this worm uses these glowing bacteria to eat the insides of caterpillars that they parasitize. The worm infects the caterpillar, regurgitates the bacteria, the bacteria start eating the caterpillar, then the worms eat the bacteria and caterpillar guts. See? Freaky. I'm glad I'm not a caterpillar. Read more about it here.

I went to plenty of other talks, but those were the ones that jumped out at me today.