Genetic structure in migratory and nonmigratory populations of Brazilian free-tailed bats

Abstract

The genetic compositions of a migratory population of Tadarida brasiliensis mexicana from Texas, two populations of this subspecies from California, one or both of which are nonmigratory, and three populations of T. b. cynocephala from Florida and Arkansas were compared using data from 22 allozymic loci. There were no statistically significant differences in allelic frequencies among the T. b. mexicana from Texas and California; the average genetic similarity among these populations was high (I = 1.000, S = 0.986), and standardized genetic variances calculated from the five most variable loci were low (F(st) = 0.014). Despite their behavioral differences, migratory and nonmigratory T. b. mexicana appear to share a common gene pool. The same loci showed close similarity (Ī = 0.996, S̄ = 0.967), but apparently greater structure (F̄(st) = 0.038) among the populations of T. b. cynocephala. The average genetic similarity between the two subspecies (Ī = 0.978, S̄ = 0.942) was within the range typically seen between geographic populations of the same subspecies. Frequencies of alleles in the single population of T. b. cynocephala from Arkansas, and the presence in this population of rare alleles seen in either T. b. cynocephala from Florida or in T. b. mexicana, suggest gene flow between these subspecies.