Tired of the BSC

In a recent blog post, Jerry Coyne argues that recent evidence that there are 4, not 1, giraffe species, is insufficient. This argument is predicated on the almighty Biological Species Concept - that if they aren't reproductively isolated, they aren't species. I'm getting tired of this purity test. To me, reproductive isolation is sufficient but not necessary. There are ample cases of reproductive isolation (to varying degrees) within species, among populations - whether it is Drosophila, Mimulus, or Pisaster. An incredible suite of dynamics affects populations and the fitness of outbreeding can be determined by far more than the on/off switch of Dobzhansky-Muller interactions. Perhaps if "species" were not our holy grail for quantifying diversity and naming it, we would recognize that reproductive isolation is not a species-level trait. Sometimes it affects populations within an ecologically and phenotypically distinct unit that is worth recognition as a "species" because it likely has a distinct function on this planet. Sometimes, clearly distinct species are not reproductively isolated - and this is the argument being made by Coyne. How can we call the 4 new Giraffa species "species" if we don't attempt to cross them?

Again, this sort of purity test avoids the rationale for why we name things. We name things because they are evolutionarily and/or ecologically distinct, with different distributions, functions, or histories on a landscape. The point of cataloguing species is not to satisfy evolutionary biologists - it is to understand how this planet works.

More to the point, naming species and drawing a boundary around them ignores the importance of ecological and evolutionary diversity within those entities. Do I think the two lineages of Notochthamalus scabrosus are separate species? Probably not. But who cares? They interact with the world in different ways, and it is important we know they exist and where they are.

Reproductive isolation is one of several traits that may be used as a criterion for distinguishing our biota. To throw away the other criteria, suggesting they are less important or less useful, biases and slows our ability to really understand what makes this planet tick, and that is far more important to me since this diversity is disappearing so quickly.