Hurray, I can once again use the internet to talk about PCMs thanks to my new PC!
So, food for thought. Kembel has a model of trait evolution and communities structured by competition, but is his model good enough? Essentially, lineages evolve their traits independent of each other and THEN are filtered to produce local communities structures. Obviously not how competitive exclusion and trait evolution actually work. I think there should be simpler and more realistic ways of getting at this... but Price's 1998 adaptive radiation model almost certainly isn't it (despite what others have said).
Later:
Right, that was a bit short on words. So, my point is that competition should have two effects that do not occur in Kembel's model: (1) the change in trait values of a lineage would be dependent on each other (divergence should be more adaptive than convergence, if they are in the same local community) and (2) extinction risk should be greater for lineages that are poorly differentiated from other lineages. Implementing (2) in a BM-like model should be relatively easy and I think it would approximate (1). No idea if it would change Kembel's results, though.
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I was thinking the same thing.
ReplyDeleteKembel's simulation is testing the power to recover a signal of phylogenetic structure that is expected given a pattern of trait conservatism on a tree, and a sorting process that occurs instantaneously based on the abundances of species.
In real life, where dispersal and colonization are not instantaneous, and where patterns of trait evolution and species interactions can affect diversification, we may expect very different patterns of phylogenetic community structure to result from these processes.
Whether this means his simulations which are testing a number of assumptions and predictions is wrong... I'm not sure. But I don't think he simulated spatial/dispersal processes very adequately.
correction: meant to say that the sorting process occurs based on the traits of species which were assembled instantaneously based on their abundances.
ReplyDeleteNot exactly a historical process.