A NEW SUBSPECIES OF POCKET GOPHER (GEOMYS) FROM TEXAS (MAMMALIA, RODENTIA, GEOMYIDAE)

Two isolated populations of pocket gophers were discovered far outside the previously known distribution of geomyids in southern Texas. These represent a new taxon, which is related to Geomys texensis in chromosome morphology and biochemical properties. The two share identical diploid number (2N = 70), fundamental number (FN = 68), and the presence of a distinctive large acrocentric X-chromosome. There are no fixed differences in any of the 18 loci analyzed with starch gel electrophoresis, when comparing the new taxon with G. texensis. However, both of these taxa share alleles at two loci that are present as fixed differences when compared to G. bursarius major. Analysis of cranial morphology indicates that the new taxon resembles G. texensis, but differs significantly in cranial dimensions of size and shape, related primarily to measurements of basal and palatal lengths and mastoid breadth. Because of the morphological distinctiveness and the extreme spatial separation (120 km) from populations of G. texensis confined to the central basin of the Edwards Plateau, we conclude that this new taxon is an isolated, relictual population of G. texensis, and is a distinctive subspecies.