[Taxacom] Why character-tracking doesn't happen?
jgrehan at sciencebuff.org
Sun Sep 14 09:53:48 CDT 2008
From: Bob Mesibov [mailto:mesibov at southcom.com.au]
> The alternative hypothesis is that the shared similarity does not
reflect common ancestry. Instead, it
> arises because there are selection pressures driving lineages towards
a common phenotype by mechanisms
> other than simple inheritance of character states.
I'm ok with mechanisms other than inheritance from a common ancestor,
but 'selection pressures' is just one possibility among several.
> In this view of things you are correct in saying, as I did earlier,
that homoplasy is something supposed
> after the fact of tree-building. It is an explanation for those pesky
non-common-ancestry cases. (IMHO
> even after a Platnick pruning of mistaken homologies there will still
be such cases.)
I still say that of itself that homoplasy is not an explanation.
> What I would like character-tracking to do is consider those cases
more carefully, rather than dismiss
> them as evolutionary noise or sampling or analytical error. If there
really wasn't a Type I error, then we
> can learn something about evolution. If there was a Type I error, then
the tree needs re-examining. Either
> way we benefit. The current custom of ignoring the details of
homoplasy seems to me to be throwing away
Perhaps so. Some characters that do not define monophyletic groups have
been shown to comprise standard tracks.
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