GENETIC AND PHENOTYPIC DIVERSITY PATTERNS IN TWO POLYMORPHIC, NEOTROPICAL ANURANS: BIOGEOGRAPHY, GENE FLOW AND SELECTION

Abstract

Geographic patterns of phenotypic and genetic differentiation among populations provide critical insight for understanding the processes that underlie the origin and maintenance of biological diversity. Fully concordant phylogeographic patterns among co-distributed taxa are an indication that landscape features promote lineage diversification. The dynamics of natural populations, however, are often more complex and organisms respond to common historical processes in different ways. I quantified variation in two co-distributed and wide-ranging Neotropical frogs, Agalychnis callidryas and Dendropsophus ebraccatus that share many ecological traits, yet differ in the geographic distribution of color pattern polymorphisms. Specifically, I compared divergence patterns across multiple populations of each species to determine whether: 1) spatial patterns of phenotypic and genetic diversity were congruent; 2) the complex biogeographic history of the Central American Isthmus has resulted in a similar evolutionary history of vicariance and dispersal; 3) landscape features limited gene flow; 4) gene flow patterns explained the geographic distribution of phenotypic diversity. I compared historical (mitochondrial DNA) and contemporary (nuclear DNA) gene flow to patterns of phenotypic differentiation. I determined cases where gene flow processes alone could not explain the patterns of phenotypic diversity, implying that selection (sexual and/or natural selection) has played a role in diversification. My results indicated that Agalychnis callidryas and D. ebraccatus have differences in their biogeographic history, population genetic structure and dispersal biology; therefore color pattern and genetic differentiation have evolved due to independent mechanisms in each taxon.