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Posted by WW on October 16, 2002 at 04:33:22:
In Reply to: a little addition... posted by vvvddd on October 15, 2002 at 20:49:00:
:Speaking of which, do you (WW) think molecular studies alone are enough to justify some recent taxonomic results? Would a combination of morphological and molecular be better or would morphological be a 'waste' of time?
:Speaking of which, do you (WW) think molecular studies alone are enough to justify some recent taxonomic results? Would a combination of morphological and molecular be better or would morphological be a 'waste' of time?
Depends on a variety of factors, including the types of molecular markers used, and also the distribution of the animals (e.g., islands vs. contiguous mainland populations).
If you have island populations and mtDNA studies show that they have been isolated for millions of years, then I see no reason against using that as the sole basis for calling them species.
On the other hand, I am less than happy about the use of mtDNA phylogeographies as the main source of evidence for calling contiguous populations different species. If two contiguous populations or sets of populations are to be considered as separate species, you need to be able to demonstrate that they are, to all intents and purposes, separately evolving lineages, which means that genetic exchange between them must be negligible. MtDNA alone cannot give you that info. Additional evidence can come either from some sort of genotyping data (microsatellites, AFLP), or from morphological data. Int he case of the latetr, this would need to be analysed critically in conjunction with the mtDNA in order to determine wether two sets of populations do or do not constitute separately evolving lineages. Personally, I am more than a little skeptical of phylogeographic studies which elevate soemthing or other to species status, and simply refer to some other source of information for morphological differences. Click on the link below for a paper in which these ideas are discussed further.
Cheers,
Wolfgang
