Female, but not male, tropical sparrows respond more strongly to the local song dialect: implications for population divergence.

In addition to the observed high diversity of species in the tropics, divergence among populations of the same species exists over short geographic distances in both phenotypic traits and neutral genetic markers. Divergence among populations suggests great potential for the evolution of reproductive isolation and eventual speciation. In birds, song can evolve quickly through cultural transmission resulting in regional dialects, which can be a critical component of reproductive isolation through variation in female preference. We examined female and male behavioral responses to local and non-local dialects in two allopatric populations of rufous-collared sparrows (Zonotrichia capensis) in the Andes of Ecuador. Here we show that female sparrows prefer their natal song dialect to the dialect from an allopatric population just 25 km away and separated by unsuitable higher elevation habitat (pass 4200 m), thus providing evidence of prezygotic reproductive isolation among populations. Males s...