GENETIC DIFFERENTIATION AMONG CHEWING LOUSE POPULATIONS (MALLOPHAGA: TRICHODECTIDAE) IN A POCKET GOPHER CONTACT ZONE (RODENTIA: GEOMYIDAE).

Genetic variation among populations of chewing lice (Geomydoecus actuosi) was examined in relation to chromosomal and electrophoretic variation among populations of their hosts (Thomomys bottae) at a contact zone. Louse demes were characterized by low levels of genetic heterozygosity (H̄ = 0.039) that may result from founder effects during primary infestation of hosts, compounded by seasonal reductions in louse population size. Louse populations sampled from different hosts showed high levels of genetic structuring both within and among host localities. Microgeographic differentiation of louse populations is high (mean F = 0.092) suggesting that properties of this host-parasite system promote differentiation of louse populations living on different individual hosts. Among-population differentiation in lice (F = 0.240) was similar to that measured among host populations (F = 0.236), suggesting a close association between gene flow in pocket gophers and gene flow in their lice.