 Biologists offer various definitions of the term ‘species’ (Claridge, Dawah, and Wilson 1997). Biologists call these different definitions ‘species concepts.’ Consider three of these concepts. The Biological Species Concept defines a species as a group of organisms that can successfully interbreed and produce fertile offspring. The Phylogenetic Species Concept (which has multiple versions) defines a species as a group of organisms bound by a unique ancestry. The Ecological Species Concept defines a species as a group of organisms that share a distinct ecological niche. These species concepts are just three among over a dozen prominent species concepts in the biological literature.