Diversification of a polyploid complex: the biogeography and acoustic communication evolution of North American gray treefrogs throughout the Quaternary

Polyploid speciation and whole genome duplications are major drivers of biological diversity. After polyploid species are formed, the interactions between diploid and polyploid lineages may generate additional diversity in novel cytotypes and phenotypes. In anurans, mate choice by acoustic communication is the primary method by which individuals identify their own species and assess suitable mates. As such, the evolution of acoustic signals is an important mechanism for contributing to reproductive isolation and diversification in this group. The North American gray treefrog complex, consisting of the diploid Hyla chrysoscelis and the tetraploid Hyla versicolor, has long been used to study reproductive isolation and research on this system has consistently driven this field forward. Here, we estimate the biogeographic history of this group, focusing specifically on the geographic origin of whole genome duplication and the expansion of lineages out of refugia following climate oscillations and retreats of the Laurentide ice sheet. We then test for lineage-specific differences in mating signals by applying comparative methods to a large acoustic data set collected over 52 years that includes >1500 individual frogs. Finally, we expand upon our results in light of recent estimates of the complex's genomic evolution to describe the history of diversification in gray treefrogs throughout the Quaternary.