David Bapst wrote -- > Let's say that there exists a worker who is measuring several different > traits across a number of species and then testing for correlations among > these traits. The first test is body size versus growth rate and they use > independent contrasts or PGLS to test for a the correlation, accounting for > phylogeny. Both of these traits are inherited, evolving variables. Now > let's say they'd like to test for the relationship between growth rate and > some metric of the anthropogenic degradation of that species' habitat. Now > what? It is even valid to apply PIC to the habitat degradation metric even > though it is not an inherited, evolving trait? It's unclear to me.
... > One explanation I know of is that when we apply phylogenetic comparative > methods to these quasi-traits to consider their relationship to another > trait, we are assuming that these variables are actually the result of some > underlying, unobserved set of traits which are evolving along the > phylogeny. I don't have an easy answer to this: it is a serious issue. One is assuming that the environmental variable is evolving along the phylogeny according to a Browian motion process. This may well not be a reasonable assumption. Joe ---- Joe Felsenstein j...@gs.washington.edu Department of Genome Sciences and Department of Biology, University of Washington, Box 355065, Seattle, WA 98195-5065 USA [[alternative HTML version deleted]] _______________________________________________ R-sig-phylo mailing list R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo