Place in taxonomy
tdib at OCEANCONSERVANCY.ORG
Mon Jul 8 15:50:44 CDT 2002
Sorry I havent replied sooner, I was on a short vacation -
Robert Mesibov wrote:
> There are numerous cases where geographical proximity DOES
> correlate well with closeness of relationship,
Sure, but the problem is trying to distinguish when it does and when it doesn't.
> where things live can help you to discount (read: "judge to be less
> plausible") trees which do justice to the character evidence but are
> biogeographically unlikely.
But only if you accept that the distribution was constrained in particular ways - a set
of assumptions that I find very hard to accept, in general, and in most specific cases.
It seems to me to be always more reasonable to view spatial distributions as
historacally mutible rather than character evidence .
> It seems to me the issue is more methodological than philosophical. Tom
> knows that there's phylogenetic evidence in spatial information, but he
> doesn't yet have a good method for extracting that evidence. He shouldn't
> claim that the evidence doesn't exist!
Perhaps it is philosophical. I actually do not think that there is phylogenetic evidence
in spatial distributions. There is geopgraphic evidence - there is biogeographic data,
but I don't think it rises to the level of phylogenetic evidence. To be evidence,
particular data must have a well-understood set of implications relative to
phylogenetic conclusions (as in character evidence - matching states indicate
common descent). The problem with spatial data is not extracting the evidence, it is
meeting the basic requirements of evidence.
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