Ensign Morituri

Hi everyone,

I am only mildly familiar with the concept of speciation, not to mention biology or any of the sciences for that matter, so thank you for your insightful responses.

demoninho and Wounded King:

No, I haven't been on either of those threads. The question arose in my mind from reading a National Geographic article on dogs and their ancestors. The article had a photograph of various breeds of dogs, including a chihuahua sitting in front of a great dane, and my curiosity was sparked.

Minnesota

As you probably now realize, since you have subsequently quoted me correctly, I never said that the "Biological Species Concept, that a species is a set of actually or potentially interbreeding organisms, been 'thrown out'"
In essence, yes.

At one time the definition of a species pretty much hung on the single idea that any organisms that could successfully breed were, by definition, of the same species. And any two organisms that could not do so could not be of the same species. Fertility/infertility, alone, was the standard measurement for defining species. As keith Rushford points out in his book, Conifers, "The traditional criterion of a species being interfertile between its members of the species and, under natural circumstances, at least partially intersterile with members of another species is subject to too many qualifications to be useful in practice."

Origian

I remember reading the same National Geographic article recently and thinking exactly the same thing. Surely, considering that prezygotic barriers to reproduction exist (one would assume anyway, considering the size difference...) between the Chihuahua and Great Dane, it can be said that they have speciated. Or do postzygotic mechanisms also have to exist?

Wounded King

Minnesota, I still can't see what you think the difference is between that Keith Rushford definition and the BSC definition. Could you clarify what you see as the distinction between reproductive isolation and whole or partial intersterility under natural circumstances.

It sounds to me as if what Rushford is saying is that the BSC is "subject to too many qualifications to be useful in practice".

I don't see in what way you think the Mayr definition differs from Rushford's definition, except in the specifics of the terminology. Perhaps we have different interpretations of what being intersterile under natural circumstances means. To me the 'natural circumstances' part allows this definition to cover pretty much any form of reproductive isolation.

Obviously the BSC doesn't work when applied to asexually reproducing poulations, lukcily there are still several other species concepts that could be used in this case.