[Taxacom] Clade age (was: Taxacom Digest)
jfmate at hotmail.com
Sat Nov 12 18:03:02 CST 2011
> So individuals at the extreme geographic limits of a distribution cannot interbreed even though their intermediaries do.
Well, it can happen. That is the basis for concepts such as ring species. The breakdown of panmixis can happen in a variety of ways.
> Yes this is the standard Darwinian toolbox. But acceptance is less the issue than how one gets there.
I am not sure what you mean. IMHO everybody´s toolbox should have a variety of tools so as to apply the appropriate one to the job. Duct tape (vicariance) can only get you so far.
> They all 'fail' because they are attempts at defining species when they are really attempts to define species boundaries using criteria that cannot apply to all species. What they are really doing is identifying parameters that are spatiotemporal (and therefore biogeographic) by which a species entity is predicted for a given time and place. Species, like any other taxonomic level, can be diagnosed. But as for 'defining' one ends up just tying oneself in obscure metaphysical knots.
Well, organisms do occupy a space so by definition their geographical location is part of the issue. Of course there are other equally important factors as well without which biogeography alone cannot work. As for species´ definitions, they are necessary not because they are real but because they force us to analyze our ideas and the reasons why we choose to do what we do, as well as allowing others to tear holes in them, a painful but necessary process. So when you make a call, testing your species against several definitions may well save you from synonym purgatory (as well as other people´s time). In the end the only taxonomic level that has any hope of being ´properly´defined are species. The rest are just tags for our convenience (hence the inherent problems with Phylocode).
“A species is what a community of taxonomists says it is.”I´m afraid it is too lonely in systematics for this concept to be of any use. :)
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