For some species, geographic clines in body size ( Brown and Thorpe 1991 Storz 2002), behavior ( Thompson 1990 Pröhl et al. Many taxa exhibit some phenotypic variation among individuals within populations, although the spatial distribution of genetic and phenotypic diversity varies substantially among species ( Hoffman and Blouin 2000 Gray and McKinnon 2007). The spatial distribution of divergent phenotypes provides insight into the relative roles of natural and sexual selection, gene flow, and vicariance in the diversification of a species ( Grinnell 1924 Ford 1971 Slatkin 1985 Brown et al. Our study underscores the fact that selection gradients vary across relatively small spatial scales, even in species that occupy relatively homogeneous environments.Īgalychnis, biogeography, color pattern, Costa Rica, Panama Although the mode of selection underlying color variation was not the focal objective of this study, we discuss the possible roles of natural and sexual selection in mediating population differentiation. These patterns indicate that phenotypic diversification is highly regionalized and can result from spatial variation in localized adaptations, geographic isolation, genetic drift, and/or evolutionary stasis. We detected 3 generalized spatial patterns of genetic and phenotypic diversity: 1) phenotypic differentiation in the presence of historical connectivity, 2) phenotypic uniformity across genetically differentiated regions, and 3) codistribution of genetic and phenotypic characters. Two phenotypic characters varied independently among isolated population groups: Flank coloration distinguished Caribbean from Pacific individuals, whereas leg coloration exhibited a more complex geographic pattern. Phylogenetic analyses revealed 5 well-supported mitochondrial DNA clades, and we infer from our phylogeny that geographic barriers have played a large role in structuring populations. We quantified color differentiation and genetic divergence among 20 populations of the red-eyed tree frog ( Agalychnis callidryas) in lower Central America. Spatial patterns of heritable phenotypic diversity reflect the relative roles of gene flow and selection in determining geographic variation within a species.
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