In my presidential address to the Society for the Study of Evolution last night, I started off, as I had to, by defining what I meant by speciation (my talk was, after all, about speciation). I said that I was using the “biological species concept” (BSC), which conceptualizes species as populations separated by reproductive isolating barriers: genetically based features, like mate discrimination and hybrid sterility, that prevent gene flow between different groups. And when I put up a slide of the BSC, I said it was the “right” species definition.
That was meant to be both funny and provocative: I know that different groups of biologists have different species concepts, and in some cases they should—you can’t use the BSC in bacteria, for example, which don’t really have sexual reproduction. But in my book Speciation with Allen Orr we note that there’s no one “right” species concept: concepts are more or less useful depending on the biological problem you’re addressing.
Since my problem is addressing the origin of distinct groups that coexist in one place without much interbreeding, the BSC is the only one that makes sense. Indeed, regardless of the species concept proposed by biologists—and there are many—when biologists go about studying the process of speciation in sexually reproducing groups, all of them, nearly without exception, adhere to the BSC. That is, when they study speciation they invariably study the origin of barriers to gene flow. So if the origin and existence of discrete groups of sexual taxa nature is the problem—why there are blackbirds and robins and crows and sparrows, all living distinctly and discretely in one place—then the BSC is the go-to concept.
I used the word “right,” of course, to make people laugh, to provoke them (after all, the meeting includes a lot of systematists, many of whom abjure the BSC), and because it’s well known that I’m a staunch advocate of using the BSC for the “species problem” described above and have been a vociferous critic of other species concepts.