>>Hi folks,

>>

>>what is the current "handling" for sibling species (morphological indistinguishable but [reproductivly] isolated (= allopatric). Are they recognized at subspecific rank today?

>>

>>Cheers,

>>Wulf

>>-----

>>http://www.leiopython.de - the white-lipped python site -

>>http://www.herpers-digest.com - herp related eBooks search -



Allopatry is geographic isolation, not reproductive isolation. If they are morphologically indistinguishable, then there is little evidence that they are different species and should not be recognized as different species. If, however, it can be shown that they have differentiated in some other way that result in reproductive isolation (for example, one population has become a polyploid and the other remains a diploid), then each should be named a different species. A good example is the Hyla chrysoscelis-Hyla versicolor species pair. They are morphologically identical, and yet reproductively isolated because one of them is a diploid and the other is a tetraploid species that has twice the number of chromosomes. Hybridization between these two species is not possible.



Of course there are some taxnomists who behave differently. They will invoke the so-called "evolutionary species concept" or Willi Hennig's "phylogenetic species concept" and call 2 allopatric populations 2 different species on the basis of as little as a single character difference between the two populations. Some taxonomists call this practice a return to "Taylor taxonomy." Edward H. Taylor was a well known taxonomist who made tremendous contributions to herpetology, but he also recognized numerous species on the basis of minor morphological differences. Many of these "species" have subsequently been placed in the synonymy of other well established species. Taylor is gone, but "Taylor taxonomy" is apparently being revived by some taxonomists. In the future, however, many of the "species" being named today on the basis of minutle morphological differences will likely be placed in the synonymy of other species.

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