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Posted by Troy H. on January 11, 1999 at 09:15:41:
In Reply to: Re: Species is only Taxonomic level that is "real" posted by SNYDER on January 09, 1999 at 10:42:40:
In your example (if two pops diverge for a time, but then reconnect and their distinctness is swamped by panmictic gene flow between the formerly separate populations), then by the Evolutionary species Concept, the two were never separate species.
However, the problem in applying species CONCEPTS to real world situations is that we are only looking at a slice of evolutionary time, and that we have to make our best educated guess, particularly concerning allopatric populations of animals such as snakes and small mammals that don't disperse easily (i.e. allopatry in birds is a different story than allopatry in herps).
Allopatry is, always has been, and always will be the toughest test of any species concept. You see, we simply cannot know the future . . . will zonata & pyro reconnect 10,000 years in the future? We just can't know, so we must do our best to interpret their "species-ness" in light of our concept of species.
Many "old-school" folks would avoid the problem of allopatry by saying that if the two pops can interbreed and produce fertile offspring, then the two are the same species . . . however, this test is in all actuality a poor measure of a species evolutionary distinctness from its close relatives . . . you see, the ability to interbreed & produce fertile offspring is by its defintion a primitive characteristic common to all the species derived from a common ancestor . . . a species must develop reproductive isolation. In many cases (e.g. leopard frogs) the two species in a group that share reproductive capability are the two most distantly related evolutionarily.
Troy
