Allopolyploidization, Niche Evolution, and Systematics of Central African Night Frogs

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Most vertebrate species are diploid: they have two sets of chromosomes, one from each parent. In some species, there is a duplication of each set leading the species to become polyploid (i.e., it has more than two sets of chromosomes). This can happen when two species hybridize and thus create a new polyploid species that contains both sets of chromosomes from each “parent” species. The newly formed species may be in competition with its parental species and may therefore evolve to occupy new environments. Competition between polyploid species and their diploid parents has been studied in plants but not in animals. This project will focus on two closely related groups of frogs from forests in West and Central Africa that are known to exhibit polyploidy: Night Frogs (genus Astylosternus) and Hairy Frogs (genus Trichobatrachus). The project will collect new data for thousands of genes from all of the species in these two groups. The researchers will analyze these data to establish the relationships among these frogs and to test hypotheses about how polyploid species compete with parental species and are potentially driven to create new ecological niches, even in relatively inhospitable environments. The results will provide new understanding about how and why polyploid species come to inhabit extreme environments. Better documentation of distributional and environmental requirements will also inform conservation efforts for six of the targeted species that are considered threatened by habitat loss. This project will train undergraduate students and develop on-line learning modules to help undergraduates understand the science of polyploid species. The researchers will lead a training workshop for scientists in the U.S. and Cameroon that will provide hands-on training for use of new tools to analyze the distribution and evolution of polyploid species.This project will advance our understanding of the processes generating polyploid species and the associated evolution of ecological niches. It will also add to our understanding of how these processes impact the formation of new vertebrate species in tropical ecosystems. The project will develop new methods to construct ancestral state reconstructions of fundamental niches on time-calibrated polyploid phylogenetic networks. These methods will be broadly applicable across polyploid plants and animals. The focal genera Astylosternus and Trichobatrachus are distributed across forest types and elevational gradients in Central Africa. They thus represent a unique vertebrate system for studying the geographic, climatic, and temporal factors that influence the creation of polyploid species through hybridization and subsequent niche evolution. Synthesis of phylogenetic relationships, species distributions, available advertisement calls, and newly collected anatomical data from CT-scanning will also facilitate a thorough taxonomic revision of these poorly known frogs, including the discovery of undescribed species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.