Systematics of the Polytypic Snake Elaphe guttata (Serpentes: Colubridae)
McFadden, Michael S.
The separation of species into subspecies has been debated and its usefulness is unclear. Subspecific classifications may be an aid to identification by taxonomists, or misapplied to incorrectly recognize organisms that may be more properly designated as species. While arguments of the species concept continue, the role of subspecies will continue to be uncertain. Newer methods for determining the relationships between taxa can be employed to examine polytypic species in which subspecies separations have been used. Mitochondrial DNA analyses were used to determine the evolutionary relationship among subspecies of Elaphe guttata withm Texas and relationships among subspecies of E. guttata m Texas, Colorado, New Mexico, Louisiana, Georgia, and Florida. Molecularsystematic analysis of the c o n snake E. guttata revealed the presence of three distinct clades; a clade composed of snakes from Florida and Georgia to the Mississippi River, a clade composed of snakes from the Mississippi River to the Austronparian Region of Texas, and a clade composed of snakes in central and south Texas extending into New Mexico and Colorado. The separations in these clades supported the current subspecific taxonomy, which is based on morphological characters. Distance measures among the clades indicate that the snakes from south and central Texas should be classified as a distinct species as recognized in 1951, and the two remaining clades should remain subspecies of E. guttata. The presence of distinct clades that agree with current morphological characters suggests, that in the case of E. guttata, subspecific taxonomic separations are useful systematic tools that describe distinct evolutionary lineages.
Corn snake, Polytypic snake, Biogeography, Species
McFadden, M. S. (2002). <i>Systematics of the polytypic snake Elaphe guttata (serpentes: Colubridae)</i> (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.