Genetic Diversification, Vicariance, and Selection in a Polytypic Frog

Abstract

Spatial patterns of heritable phenotypic diversity reflect the relative roles of gene flow and selection in determining geographic variation within a species. We quantified color differentiation and genetic divergence among 20 populations of the red-eyed tree frog (Agalychnis callidryas) in lower Central America. 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. 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. 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. 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. 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. Our study underscores the fact that selection gradients vary across relatively small spatial scales, even in species that occupy relatively homogeneous environments.

Cryptic Population Structuring and the Role of the Isthmus of Tehuantepec as a Gene Flow Barrier in the Critically Endangered Central American River Turtle

“…In the lowland habitats in Central America the red-eyed tree frog ( A . callidryas ) shows pronounced genetic structure across the Cordilleran Mountains [14]. Within the geographic range of D. mawii , the genus Bufo has different genetic lineages to the West and East of the Isthmus of Tehuantepec and Sierra de Santa Marta [12].…”

“…For individuals with the divergent mtDNA haplotype 1D (up to 2% divergent from all remaining haplotypes [14], a genetic distance indicative of species-level distinction in some turtle lineages [16]), it was not straightforward to interpret the results based on nuclear loci. While those individuals appeared clearly divergent in the FCA analysis (Fig.…”

“…Even species occurring in apparently homogeneous lowland habitats in Mesoamerica can exhibit population genetic structure when movement is inhibited. The red-eyed tree frog ( Agalychnis callidryas ) of lower Mesoamerica shows pronounced genetic structure not only across the Cordilleran Mountains, but also within each of the contiguous Caribbean and Pacific coastal forest habitats [14]. Dermatemys mawii might therefore show previously unknown genetic structuring across its range, with potential conservation implications.…”

Patterns of genetic diversity in the critically endangered Central American river turtle: human influence since the Mayan age?

“…Even species occurring in apparently homogeneous lowland habitats in Central America can exhibit population genetic structure when movement is inhibited. The red-eyed tree frog (Agalychnis callidryas) of lower Central America shows pronounced genetic structure not only across the Cordilleran Mountains, but also along the Caribbean and Pacific coastal forests (Robertson and Zamudio 2009). On the other hand, species with lower habitat specificity and thus greater freedom of movement exhibit less structure: the Coahuilan box turtle (Terrapene coahuila) is a semi-aquatic species capable of stepping-stone movement among regional wetlands and exhibits high levels of gene flow (Howeth et al 2008).…”

Variation in male spermiation response to exogenous hormones among divergent populations of Red-eyed Treefrogs

“…data). However, genetic analyses using nuclear and mitochondrial DNA indicate that these populations represent a single intraspecific lineage [15, 16]. …”