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RE: Should there be aGenus reclassificat

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Posted by: CKing at Fri Apr 18 21:36:00 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]  
   

>>Hi,
>>
>>It's important to realize that most current taxonomic work is done in a cladistic framework, and using the evolutionary species concept, meaning that evolutionary history and genetic distinctness is more important than biological interactions. There's a lot of argument among scientists over whether or not this is a good thing, but it's the way most papers are written these days.

Yes it is unfortunate. Most biologists still accept the biological species concept, and yet a large number of the young taxonomists (the upstarts) are using the evolutionary species concept. That creates controversy and endless arguments whenever someone proposes a new species on the basis of the evolutionary species concept.

>>Hybridization in captivity is generally not taken as evidence that two species should be considered one; even frequent hybridization in nature (as in American, southern, and Fowler's toads, or the five-lined skink group) is not sufficient if the species involved maintain their distinctness in nature.
>>
>>It's been a while since I read any of the Emydidine classification revisions, but as I recall the reason Clemmys was broken up into Clemmys, Actinemys, and Glyptemys was because Terrapene arose from within Clemmys according to the researcher's cladogram, thus rendering Clemmys (in the older, more inclusive sense) paraphyletic. There were two possible nomenclatural revisions: 1) include the bog, wood, western pond, and spotted turtles together with the box turtles in one big genus, or 2) split Clemmys up. The researchers went with the latter option, probably because they wanted to leave the well-defined genus Terrapene alone.

It is quite obvious from those cladograms that the North American emydidine turtles is a clade that evolved from a common ancestor which migrated from Eurasia. The genus Clemmys is a paraphyletic genus that is close to the base of this clade. Breaking up this genus is silly since the species in this genus form a rather homogeneous group morphologically. The cladists' intolerance of paraphyletic taxa rears its ugly head again. They should simply leave paraphyletic taxa alone, as taxonomists have done for centuries, instead of generating taxonomic chaos continuously.

>>Now, as for Emydoidea, I don't believe any one has suggested it should be included with any of the former Clemmys species; it is usually shown as being a basal sister lineage of the Clemmys-Terrapene lineage. In some reconstructions it is shown as the sister species of Emys orbicularis, the European Pond Turtle, so it could be moved to that genus, rendering it Emys blandingi.
>>
>>I hope this was helpful.

I hope that cladists would simply come clean and tell us up front why they are splitting taxa. Tell us that the new taxa is proposed because they are following Hennig's lead and that Hennig says paraphyletic taxa should be disqualified. What many of them are doing is simply dishonest. They claim that the taxa they split is "not monophyletic." That deliberate choice of terms is deceptive because to most biologists "not monophyletic" is synonymous polyphyletic. Since no biologist would knowingly recognize polyphyletic taxa, many biologists are thus deceived into accepting the new taxonomic proposals as valid. If the cladists would confess that they are proposing the new arrangement because the old taxon is paraphyletic, the new proposal would have been ignored by a large number of biologists, since many biologists, unlike the cladists, make no distinction between paraphyletic and monophyletic taxa and accept both as valid.

Hence, cladists should make clear, if they are honest, whether the taxa they propose to split is paraphyletic or polyphyletic, instead of deliberately lumping both types of taxa under the umbrella term "not monophyletic."


   

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