AGE AND MOVEMENT OF A HYBRID ZONE: IMPLICATIONS FOR DISPERSAL DISTANCE IN POCKET GOPHERS AND THEIR CHEWING LICE.

Historical flood records for the Rio Grande Valley of New Mexico suggest that a pocket gopher (Thomomys bottae) hybrid zone previously thought to be 10,000 years old may actually be closer to 50 years old. Measured zone width (defined genetically) is consistent with the hypothesis of recent contact, if we assume a reasonable dispersal distance of approximately 400 m/year for pocket gophers. A five-year study of movement of the contact zone between the two species of chewing lice that parasitize these pocket gophers also is consistent with the hypothesis of recent origin of the zone.