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Re: Species [arbitrary to a degree]
Asexual reproduction is certainly a problem for species concepts.
However, I think it is even more of a mistake to so quickly dismiss the
important implications of "ring species" where populations (e.g.,
subspecies) can interbreed with adjacent populations just fine, until the
species circles around (circumpolar, around a mountain range or whatever),
and the populations at the end of the ring can no longer interbreed at all.
I've always regarded the ring species as a prime example of the
"fuzziness" of the boundaries between species "in space". Throw in the
fourth dimension and the fuzziness gets even worse (which makes
paleontological species all the more controversial and difficult).
The continuity of life is a fact that cannot be escaped even at the
species level (or at the population level for that matter). Even species
are somewhat arbitrary at some level, and the arbitrariness of genera is in
some ways qualitatively the same, but quantitatively very much magnified.
So maybe we should abandon species as well????? Obviously not.
Perhaps it is just better to admit ranks are all human constructs on some
level, and get on with the job of minimizing the arbitrariness at every rank
as best we can. Arbitrariness can't be eliminated, and therein lies the
blind side of strict cladism. It's a bit like the Heisenberg Uncertainty
Principle of biology, and there is no getting away from it-----so we have to
accept it and do the best we can.
It therefore seems a good time to end the fruitless struggle to
totally eliminate formal paraphyly from classifications, as it is a natural
consequence of the continuity of evolution. The total elimination of formal
paraphyletic groups from classifications is not only fruitless, but
unnatural. However, that is just my opinion, but hopefully some of this
will make some sense to some strict cladists down the road. Just think
about it from time to time.
T. Mike Keesey wrote:
On Thu, 18 Oct 2001, Graydon wrote:
> A species is a population where there is no genetic restriction to the
> degree of the common descent among the next generation from any member
> of the species -- they can all mate effectively with each other, given
> the opportunity.
What about asexual organisms?
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