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.

多倍体物种形成与全基因组复制（whole genome duplication）是驱动生物多样性产生的核心动力。多倍体物种诞生后，二倍体与多倍体谱系间的相互作用可催生新型细胞型（cytotype）与表型（phenotype）层面的额外多样性。在无尾目（Anura）动物类群中，基于声学通讯的配偶选择是个体识别同类、遴选适配配偶的核心途径。故此，声学信号的演化是该类群建立生殖隔离、实现物种分化的关键机制之一。北美灰树蛙复合群由二倍体Hyla chrysoscelis与四倍体Hyla versicolor组成，长期以来被应用于生殖隔离相关研究，该研究体系始终推动着相关领域的发展。本研究重建了该类群的生物地理演化历史，重点关注全基因组复制的地理起源，以及劳伦泰德冰盖（Laurentide ice sheet）消融与气候波动后，谱系从避难所向外扩张的过程。随后，我们依托跨越52年收集的涵盖1500余只个体的大型声学数据集，运用比较分析方法检验了不同谱系间配偶信号的特异性差异。最后，我们结合该复合群近年的基因组演化研究结果，进一步阐释了第四纪（Quaternary）时期北美灰树蛙的物种分化历史。