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Re: Koreanosaurus (regarding PDFs instead of forelimbs)



On Thu, Oct 21, 2010 at 6:45 AM,  <vultur-10@neo.tamu.edu> wrote:
>
> Several reasons, but primarily because I think as we find more and more cases 
> of reticulate evolution (hybrid speciation, etc.) a purely phylogenetic 
> classification will get messier and messier. It *can* be done, but it 
> requires weirdnesses like interlocking taxa -- which IMO are more trouble 
> than they're worth. And bacteria are so full of horizontal gene transfer I'm 
> not even entirely convinced that phylogeny is even a particularly useful 
> starting point, since it's *so* unstable.

Phylogenetic taxonomy requires you to do two things first: determine
your taxonomic units, and determine what constitutes "ancestry". You
are pretty free to do this however you see fit (within reason); the
rules only lock in after you have taken these first steps.

> I think taxonomy should follow phylogeny in 99% of cases - at least for 
> eukaryotes and less-riddled-with-gene-transfer prokaryotes, but 
> taxonomic-units should be kept 'at one remove' from clades -- which are 
> actual biological units & therefore messier than desirable in a 
> classification, which is ultimately a tool, and thus utility is the most 
> important thing.

Again, determining taxonomic units is not part of phylogenetic
taxonomy. It is a prerequisite, but not a part.

> (The other case -- beyond reticulate evolution and such -- where I think 
> taxonomy should depart from phylogeny is to preserve certain names of such 
> wide use that changing them would only introduce confusion -- moving 
> *Drosophila melanogaster* to *Sophophora* would never be universally 
> accepted, so a paraphyletic *Drosophila* is probably the best of the 
> available options.)

This is more of a nomenclatural issue than a taxonomic one. Seeing as
it involves genera, it is not under the purview of phylogenetic
taxonomy. (Or, at least, it shouldn't be. There is a movement to use
clades in place of genera, but this is untenable.)

> Also, I have inherent qualms with *any* fundamental change this late in the 
> game, after ~250 years of taxonomy. It's unstable enough as is, and a lot of 
> old names would be uprooted for no real reason.

"It's unstable enough as is." That is precisely the motivation behind
PhyloCode. Stabilize the definitions of clade names, and any further
unstability will at least be about something interesting (phylogeny).

-- 
T. Michael Keesey
http://tmkeesey.net/