 Biologists have been, and are still, deeply divided over the species category (Ereshefsky 1992b; Wheeler and Meier 2000; Coyne and Orr 2004; Wilkins 2009). Consider Ernst Mayr’s famous biological species concept (BSC). He writes, “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups” (Mayr 1963, 89). There are lots of concerns regarding the BSC (Ehrlich and Raven 1969; Sokal and Crovello 1970; Van Valen 1976; Wiley 1978). Asexual organisms do not interbreed. Thus, on the BSC, there are no species of asexual organisms. Many species exhibit some introgression, and thus cannot be distinct species. Last, the BSC is extremely difficult to apply to species in the fossil record since sex organs do not normally fossilize, and reproductive behavior is difficult to corroborate. In light of the problems with the BSC (and for other reasons), biologists have put forward other species concepts. Species pluralism is the claim that there is no single correct species concept that classifies organisms exactly the same (Ereshefsky 1992a); rather, there are several correct species concepts. That is, for some organisms, different species concepts will correctly place them in distinct species. Species monism is the claim that there is a single correct species concept. Some allege species pluralism is temporary because we will eventually find the single best concept (Hull 1999). The debate between pluralists and monists rages on (Wilson 1999). 