Cladistics and "Eclecticism"
rjensen at SAINTMARYS.EDU
Tue Feb 5 13:32:59 CST 2002
> The branch with two terminals
> ---- |
> now has three terminals
> ---- |
Since we're getting into improbable, but certainly not impossible, examples,
let's consider this. In my example above, the isolated population (C) is the
result of autopolyploidy with a single propagule getting established and
founding the new population. C has both morphological apomorphies (polyploidy
often yields these) and is a "good" biological species. A, as a species-level
taxon, no longer exists. So, we now have two species and let's suppose that for
the next two centuries C and A undergo separate evolutionary fates. The
population of C begins to spread locally and some additional genetic apomorphies
evolve. On the other hand, during the same time A experiences stabilizing
selection that results in no apomorphies that could be used to differentiate
extant A from A of 200 years ago. Then, the habitat in which C is surviving
(ANWR?) is destroyed and C becomes extinct. What is A now that C is extinct?
With no apomorphies to differemtiate it from its ancestor (pre-C A), it's still
A. Would this be a case of extinction (as a taxon) not being forever?
Such a scenario may be occurring right now, given the fact that there are
instances of relatively recently derived auto- and allopolyploids that currently
have limited geographic ranges.
Richard J. Jensen TEL: 219-284-4674
Department of Biology FAX: 219-284-4716
Saint Mary's College E-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556 http://www.saintmarys.edu/~rjensen
More information about the Taxacom