A month to go

I have a month and three days until my orals. Since the month is February, this means I have a month left. I presented my prospectus to an orals-preparation class we are required to take in my department on Monday. I am supposed to present my research without recourse to PowerPoint, which is challenging, but a good skill to acquire. My department, though, is interdisciplinary, which meant that I am not sure how much of my audience really understood or was interested in hearing about speciation and mutualisms and the geography of the South Pacific; audience disinterest is definitely not helpful when you are trying to practice giving a good speech. I got a lot of interesting questions at the end, though. One fire ecologist asked about competition between pollinator species for the same host plant leading to differences in absolute and realized niches, something I had never thought about. The social science students wanted to know about the cultural significance of the organisms I study to the Polynesians, and the ethics of collecting specimens in a "post-colonial context". (French Polynesia is not post-colonial, it is a colony!)

In a phylogenetics class I am taking, we had an awesome class debate on the selection vs. constraint argument in evolution. The debate is an attempt to resolve the cause of the stasis we see in the fossil record and the fact that we can conceive of many presumably adaptive phenotypes that do not exist (plants that can walk around, four-legged vertebrates with an extra pair of wings like angels). Basically the argument is between those who view all traits of all organisms constantly under natural selection (so that these intermediate, transitional phenotypes are maladaptive and selected against) and those who argue that organisms get stuck in particular developmental pathways, which do not mutate easily, and lack the requisite variation to ever evolve into many new phenotypes that might be adaptive. A possible reconciliation to this idea is that the "canalization" we see in development is due to selection against embryos with mutant developmental pathways in utero or in the egg, so that we never see this variation in nature (the fact that this reconciles the two camps, however, does not mean it is right).

Anyway, one idea that came up in class is the contingency thought experiment posed by Stephen Jay Gould: if you could rewind the tape of life back to the beginning and play it again, would the history of life be the same? One way to answer this question is to think about which adaptations have evolved repeatedly (convergently) in the history of life. These might be more likely to reevolve. From this perspective, innovations such as endosymbiosis, multicellularity, and both autotrophy (either photosynthesis or some kind of chemosynethesis, but not necessarily both) and heterotrophy are likely to evolve repeatedly. The same is true for terrestriality and life in the deep sea, because multiple lineages of organisms have colonized both habitats. But animals only evolved once; the same is true of fungi, and of green plants (green algae plus land plants), so groups sharing the characteristics of these organisms are not as likely to be inevitable. Assuming you had animals, complex eyes, the ability to fly, and eusociality would be more likely to evolve than human-like intelligence, or a backbone, or jointed legs and an exoskeleton, because the former traits have evolved repeatedly in multiple groups of organisms. There are lots of pitfalls to this thought experiment; many of the traits are dependent (so far as we know) to other traits, for instance. And some of these life-plans (like animalness or funginess) might have only arisen once because they so successfully filled their adaptive zones to the exclusion of all other organisms.