[Taxacom] The Reality (or not) of Species (again!)`

Curtis Clark jcclark-lists at earthlink.net
Mon Sep 15 21:41:53 CDT 2008


On 2008-09-15 03:50, Neil Bell wrote:
> The problem I have with this (I didn't have a problem with most of what 
> you said) is that it seems to conflate perspective with a continuum of 
> reality/unreality, or of accuracy of representation. It's not that the 
> phylogenetic perspective is "broader and cruder" (and so further removed 
> from "reality"), but rather that it *really is* the more accurate 
> representation of relationships at the level at which it operates. The 
> relationships between a group of single exemplars (even if they are 
> treated as individuals)  from different families are nearly always 
> genuinely hierarchical. It doesn't matter in this  context if some of 
> them are members of ambiguously differentiated species complexes; any 
> individual you selected from that complex would have the same 
> relationship to the exemplars from the other families as any other 
> (irrespective of whether you could accurately reconstruct it). To claim 
> that this perspective is "cruder" seems to me just a bias of 
> perspective. The hierarchical structure is genuine (a product of the 
> fact that at *some* level of differentiation there is a permanent 
> severing of gene flow between lineages, lateral transfer excepted) and 
> you need the tools of phylogenetics to observe it. The fact that the 
> relative relationships of these individuals ultimately derive from 
> processes that cannot be characterised in the same manner does not make 
> them less "real", or justify this statement:

Yeah!  What he said!

Exactly.

> Of course a phylogenetic study conducted within a single genus in which 
> half of the supposed species are hybrids or populations having 
> significant gene flow between them will be fundamentally flawed, but the 
> error is in the application of the method, not in the method.

I was actually working on a situation like that (fewer species of hybrid 
origin, but a lot of hybridization) when I got pulled into other things 
in the late 1990s. It requires multiple lines of inference. Slavish 
adherence to any single approach is doomed to fail. But cladistics was a 
useful tool in the toolbox.


-- 
Curtis Clark                  http://www.csupomona.edu/~jcclark/
Director, I&IT Web Development                   +1 909 979 6371
University Web Coordinator, Cal Poly Pomona




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