[Taxacom] Clade age (was: Taxacom Digest)‏

John Grehan jgrehan at sciencebuff.org
Sun Nov 13 09:16:57 CST 2011

From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Jason Mate

> 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.

So there is the point, that species can comprise non-interbreeding elements.

> 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.

What I mean is that in usual practice vicariance and dispersal are overlain according to some preconceived notion rather than being discovered through biogeographic evidence.

> 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 

And time

> so by definition their geographical location is part of the issue. 

I said sptatiotemporal, not geographical.

> Of course there are other equally important factors as well without which biogeography alone cannot work. 

???? Explain

> 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. 

But as above, people are in practice not defining species, but specifying parameters for their recognition in space and time.

> 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). 

But in practice this 'testing' is only against species diagnostics, not definitions.

> 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).

If only it were that simple, but species definition comes up again and again, so after all this time the hope of being 'properly' defined seems as elusive as ever.

> “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. :) Best Jason

It’s the practical reality, whether one is a community of one or of more.

John Grehan


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