A new species of indigo snake from north-western Venezuela (Serpentes : Colubridae : Drymarchon)

INTRODUCTIONThe last two decades have seen a revival in interest inthe alpha taxonomy of many groups of animals. This re-surgent interest can be traced to several factors,including the increasing awareness of the extreme rateof extinction caused by human activities, the develop-ment of new molecular (e.g. Avise, 1994) and numerical(e.g. Thorpe, 1976, 1987) methods for the investigationof species-level systematics, and a widespread shiftfrom process-based species concepts (in particular, thebiological species concept) towards historical con-cepts, such as the evolutionary and phylogeneticspecies concepts (Wiley, 1981; Cracraft, 1989; Frost &Hillis, 1990). In general, the current trend has been to-wards the recognition of clearly distinct taxa as separatespecies rather than subspecies, without undue concernfor often untestable questions of reproductive compat-ibility.During this paradigm shift, it has become apparentthat the use of the biological species concept – whichgroups similar populations together on the basis of es-tablished or assumed reproductive compatibility – islikely to result in a serious underestimate of biologicaldiversity and a misrepresentation of phylogeny(Cracraft, 1989). A number of studies have found thatgroups of populations formerly regarded as subspeciesof a single species in reality represent divergent and in-dependently evolving lineages, which should be giventaxonomic recognition at the species level.In many long-recognized, widespread, polytypic spe-cies, conspecificity of the various subspecies has neverbeen investigated, but has become fixed in the literaturethrough a three-stage process. The three stages are aninitial plethora of species described independently forvarious “forms” (usually in the 19