on 12/31/00 12:58 AM, Tony Gamble at [EMAIL PROTECTED] wrote:
> Also, be careful of applying the term "species" to uniparental
> organisms. You may be offending some closet disciples of Hennig
> on the list;)
Thanks Tony. I had read that paper too, but many years ago (did an honors
paper in grad school on evolution of parthenogenesis in reptiles). In terms
of "species", following the lineage species concept, there is no other word
that fits here. Hennig might have trouble because a branching node may not
easily occur... yet I can't help but think that if there is ANY variation
then eventually a branch point in the old Cnemi phylogeny will occur. Of
course, the problem comes when all the various hybrid forms of, say,
uniparens, are given the same species name when they clearly do not
interbreed. If truly following the lineage species concept (which appears
to me to be consistent with Hennig's cladistics, if not all the others
since) then each hybrid form of a unisexual would be a unique species. It
is sort of bothersome to me when I read from various authors that asexuals
are an "evolutionary dead end". I mean, consider that the majority of
uni-celled organisms are asexual and most plants have at least an asexual
portion of their life cycle. I suspect nobody would argue that bacteria
evolve (antibiotic resistance, for example) and certainly plants evolve.
Within the animal kingdom asexual forms occur in nearly every phylum... all
of which evolve. so long as variation occurs, evolution is happening.
Additionally if there is variation then Selection can occur. One hybrid
form of "uniparens" may be selected over others, possibly resulting in
extinction of the others. Who knows how many times this has already
happened. Or, one spontaneous mutation may have selective advantage over
the others (this could result in one of those branch points (nodes)
cladistic species concept requires). Though, admittedly, it will happen at
a much slower rate than with sexually reproducing species.
Greg
--
Gregory J. Watkins-Colwell
Dept. of Biology
Sacred Heart University
5151 Park Avenue
Fairfield, CT 06432
and
Yale Peabody Museum
Dept. of Vertebrate Zoology
170 Whitney Ave
PO Box 208118
New Haven, CT 06520-8118
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