The nature of cladistics [was: Whooper; Canadian geese split; paraphyly]

Curtis Clark jcclark-lists at EARTHLINK.NET
Thu Nov 18 08:16:30 CST 2004

on 2004-11-18 05:43 Thomas G. Lammers wrote:
> I don't understand.  Are you saying that when someone performs a
> phylogenetic analysis of the species comprising a genus, that he or she is
> NOT attempting to reconstruct patterns due to population-level
> phenomena?  Are you saying that the two forks of a cladogram at this level
> do NOT represent the establishment of some sort of reproductive isolation
> between the sets of populations represented?

My other post makes it clearer, but basically the idea is this.
Phylogenies are built of species. As one approaches the species level,
the tools of phylogenetic reconstruction become less and less useful,
until at some point "you're not in phylogeny any more". To me, this is
the very most interesting part of evolutionary biology--the "phase
transition", if you will, between population-level phenomena and
clade-level phenomena in my estimation is our best indication of what
species actually are. And it is in this context that I roll my eyes when
people talk of "paraphyletic species". Cladistics is a "whole 'nother
planet" because it deals with evolution at a different level.

> And I thought I could expect courtesy from mine.

Perhaps my irritation at the insinuation that cladists don't pay
attention to the body of work at the population and species levels made
me especially grumpy. I'm willing to call it even.

Curtis Clark        
Web Coordinator, Cal Poly Pomona                 +1 909 979 6371
Professor, Biological Sciences                   +1 909 869 4062

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