Paolo Piras wrote --
Citing http://www.r-phylo.org/wiki/HowTo/Ancestral_State_Reconstruction: Using Felsenstein's (1985) phylogenetic independent contrasts (pic); This is also a Brownian-motion based estimator, but it only takes descendants of each node into account in reconstructing the state at that node. More basal nodes are ignored. I THINK that, on the opposite, more basal nodes are NOT ignored in gls and for this reason results can differ slightly I'm wrong?
The contrast algorithm if continued to the root, makes the correct ancestral reconstruction for the root. You are correct that values for higher nodes in the tree are not the correct ML reconstruction for those nodes. If the tree is rerooted at any interior node and the algorithm used for that, then that node's reconstruction will be correct. There are ways of re-using information so that the total effort of doing this for all interior nodes will be no worse than about twice that of a single pass through the tree. However people may prefer to use PGLS, which if properly done should give the proper estimates for all nodes. There is some discussion of this in Rohlf's 2001 paper in Evolution. Joe ---- Joe Felsenstein, j...@gs.washington.edu Dept. of Genome Sciences, Univ. of Washington Box 355065, Seattle, WA 98195-5065 USA _______________________________________________ R-sig-phylo mailing list R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
