The Evolution of Sex

The 'Evolution' meeting is quickly coming to a close here in Portland. I'm presently blogging from the second last session of the meeting while Marc Johnson gives a fascinating talk on the functional evolutionary loss of sex, via the loss of recombination and segregation, in the evening primrose genus. Among evening primroses (Oenothera) 16% of species have functionally lost the ability to sexually reproduce - but this loss is associated with reciprocal translocations among chromosomes rather than with polyploidy, as it is in most asexual plants. This allows him to study the evolutionary loss of sex independently of the evolution of increased ploidy number. Evidently, asexual species pay a high cost of asexuality in terms of their susceptibility to generalist herbivore insects - although they also exhibit a decreased vulnerability to specialists herbivores (though the underlying mechanism seems a little unclear). In addition, he has found the intriguing, and somewhat counterintuitive, result (but one that had been predicted by some prior theory due to J. Felsenstein) that speciation rates are higher in functionally asexual lineages than in sexual lineages. Extinction also seems slightly elevated in asexual lineages, although this effect was non-significant.

Calibrating Phylogenies from the Fossil Record

Still at "Evolution 2010," we just saw a great talk by Charles Marshall, formerly at Harvard but now at UC Berkeley, about calibrating molecular phylogenies using the fossil records. This is a much more complicated problem that it would seem at first glance because: 1) the maximum likelihood estimate of a node age based on a fossil series from the descendant lineage is biased (towards the present); 2) an assumption that fossilization is temporally random allows for a simple correction to the maximum likelihood estimate - but this assumption is (invariably) violated in empirical data; 3) fossils are not only temporally, but also geographically, non-random; and, finally, 4) the rock record is globally incomplete in some geological eras. Charles's talk included some fantastic graphical simulations of sedimentation and "de-sedimentation" (the removal of previously deposited sediments) as ocean sea levels rise and fall over geological timescales. Evidently, though, in spite of these significant complications, there is still hope that the use of fossil calibrations can improve molecular phylogenetic estimates of species divergence dates. As usual Charles was an intensively engaging speaker and gave a great seminar!

"Dude Looks Like a Lady"

The third day of the 'Evolution' conference is officially completed and it was a good one! Among the highlights for me today was a great talk by Graham Slater (a postdoc with Mike Alfaro) about approximate Bayesian computational methods for estimating diversification and phenotypic evolutionary rates from unresolved phylogenetic trees. I think this general approach will probably have considerable utility in this and other problems for years to come.

I also saw a fantastic talk by Jeanne Robertson about courtship and aggressive behavior in dark and white sand dwelling lizards. White sand dwelling lizards have evidently evolved light colored dorsal coloration, obviously for crypsis. However, perhaps even more interestingly, in staged encounters white sand males nearly as often tried to court dark sand males as they tried to fight them. The confusion was one way, however, and Jeanne provided some excellent video of a dark sand male attacking a confused, and simultaneously courting, white sands individual. This unusual tendency is apparently due to a pleiotropic effect that dark dorsal coloration appears to have on ventral patch size - an effect that makes their ventral patches of dark sand males not much larger than the analogous patch on white sand females. So, as Jeanne so elegantly put it in the title of her talk: in white sand lizards, "Dude looks like a lady!" (For the record, Steven Tyler of Aerosmith is pictured above because that "Dude" really does "look like a lady!")

Portland 2010

The first two days of the meeting have been a blast, capped so far by a thought provoking ASN presidential address by Jonathan Losos and a picnic this evening at the Oregon Zoo. However, in terms of pure irony the most amusing experience thus far was the discovery by Carlos Botero and I (shortly after our arrival) that the Oregon Convention Center is simultaneously hosting the 'Evolution' joint meeting (as you no doubt already know) along with the 'Oregon Christian Home Education Conference.' Note, particularly for non-American readers, that one of the primary reasons children are homeschooled in the United States is so their parents can avoid teaching them about evolution (e.g., refs here and here). Luckily I had the foresight to snap a picture (above), as their conference ended this evening.

Blogging Evolution 2010 in Portland Oregon

It's that time again - the annual joint meeting of the Society for the Study of Evolution (SSE), the American Society of Naturalists (ASN), and the Society of Systematic Biologists (SSB), commonly referred to as the "Evolution meeting" will be held from today through June 29th in Portland, OR. Dechronization bloggers Glor, Igic, Harmon, and myself are all attending, so we should be able to put up a few posts during the conference. Not to miss tomorrow: Joe Felsenstein's 9am talk on "A comparative method for discrete and continuous characters using the threshold model and MCMC." I look forward to witnessing the famous "Felsenstein effect" described by Rich at Moscow's meeting last year. Please post other must-see talks in the comments.