Species: Turning a conundrum into a research program

The most appropriate ontological basis for understanding the role of specie s in evolutionary biology is the Evolutionary Species Concept. The ESC is n ot an operational concept, but one version of the Phylogenetic Species Conc ept is. Linking the ontology of species with the epistemological basis of a ctual biological studies requires that we specify both a discovert mode for identifying collections of organisms that we believe are evolutionary spec ies, and a series of evaluation criteria for assessing those entities we ha ve discovered. Simply naming a collection of specimens, no matter how stron g one's evolutionary beliefs, is not sufficient for declaring that evolutio nary species have been discovered. All operational historical species conce pts represent discovery modes with minimal evaluation criteria; all operati onal nan-dimensional species concepts represent evaluation criteria that do not specify discovery modes. Thus, both categories of knowledge are necess ary and neither is sufficient for assigning species status. This leads natu rally to a hierarchical research program in historical ecology, beginning w ith phylogenetic analysis of a group of entities postulated to be evolution ary species, which provides a productive arena for our arguments about spec ies concepts.