Farewell to Species - reticulation

[Thomas DiBenedetto]

Curtis Clark wrote:
when ancestral species are "still around" (in the tokogenetic continuity
sense), it muddies the waters for them to become higher taxa when many of
us are still (productively) using other species concepts.
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But ancestral species are never really "still around" in that sense. If the
lineage has diverged (even if you wish to call it "budded") then you have a
Y shaped lineage (even if you concieve of one of the arms as being much
thicker or longer than the other). If you wish to place the organisms that
you encounter in the field, they will be referred to one of the arms of that
"Y" (even if one is not diagnosable with an apomorphy). The stem refers to
organisms that lived previous to the divergence. So I dont think we really
have much of a problem with ever having to refer living organisms to higher
taxa only.
It is true of course, that we are probably always going to run into
complicating problems as a result of the fact that the word "species" has
taken on many different meanings. I have always wondered why biologists from
many sub-fields have felt compelled to try to "define" the term species in
ways that make sense to their field, instead of trying to _explain_ in the
terms of their field, the species delimited by taxonomists and systematists.

I always thought that it was our term, and we should fight for it. To me, it
is a group of critters that we can infer to be a terminal lineage. I think
that is pretty consistent with the largest tokogenetic network or the
smallest historical individual or any of the other phylogenetic definitions
recently proposed. But the talk of isolating mechanisms or the loss of
potential inter-fertility etc. seems to be secondary explanations of
terminal taxa, and should not take precedence.

Tom DiBenedetto
tdib at dccmc.org