AN ANALYSIS OF THREE HYBRID POPULATIONS OF POCKET GOPHERS (GENUS THOMOMYS).

Abstract

Zones of hybridization between populations of vertebrates have long been recognized and have been studied by numerous workers. Such studies have contributed to our understanding of evolutionary processes, particularly with regard to speciation. Yet certain aspects of hybrid zones still appear to be little understood, especially those concerned with the dynamics of these zones. Most previous studies involved birds and amphibians. Very few examples have been reported for mammals (McCarley, 1954 and Rudd, 1955). Therefore the study of certain populations of pocket gophers of the genus Thomomys which represent examples of hybrid zones is of interest. In a study of the distribution of pocket gophers in California, series of specimens were collected from three hyrid zones involving four subspecies of Thomomys bottae (Eydoux and Gervais) and Thomomys townsendii relictus Grinnell. Specimens from the first hybrid zone were collected in the Honey Lake Valley on the Garnier Ranch about 3 miles southwest of Herlong in April, 1963. Here the range of T. bottae canus Bailey comes into contact with that of T. t. relictus. Specimens from the second hybrid zone were collected in Lassen County during November, 1961, and April, 1962, at a point along Gold Run Creek where it enters the Honey Lake Valley. This point marks the contact of the ranges of T. bottae saxatilis Grinnell and T. t. relictus.