GENETIC DIFFERENTIATION BETWEEN POPULATIONS OF HUTTON VIREO (AVES, VIREONIDAE) IN DISJUNCT ALLOPATRY

We used starch-gel electrophoresis to analyze genetic variability at 33 loci in two populations of the Hutton's vireo (Vireo huttoni) representing coastal and interior groups of subspecies. Both V. h. huttoni (California) and V. h. stephensi (Arizona) showed reduced polymorphism. These populations are distinguished by a fixed allelic difference at the Gpi locus; Nei's D (0.031) is correspondingly large for subspecies of birds. Wright's F(ST), at 0.614, is the largest reported for conspecific populations. Using Slatkin's (1985) rare allele method, we estimated that one migrant is exchanged between coastal and interior populations every 11 to 36 generations. The isolation of these populations probably antedates the late Wisconsin glacial maximum (18,000 YBP), and their strong genetic divergence indicates essential evolutionary independence.