Genetic varation and diferentation in mexican populations of common bushtanagers and chestnutcapped brushfinches

Abstract

Genetic differentiation among four Mexican populations each of Common Bushtanagers (ChLorospingus ophthalmicus) and Chestnutcapped Brushfinches (Atlapetes brunneinucha) was evaluated using allozyme electrophoresis. In both species, although levels of withinpopulation variation are moderate, amongpopulation variation is extreme, including fixed differences among populations. Genetic variation is significantly reduced in some populations on the smallest habitat islands. Differentiation is apparently unrelated to geographic distance among populations, and effects of habitat island size and isolation on genetic differentiation are not clear. Populations of the Sierra de los Tuxtlas in Veracruz, however, are strongly differentiated in both species.