Date of Award
8-1-2025
Degree Name
Master of Science
Department
Biological Sciences
First Advisor
Brown, Jason
Abstract
Amazonia has gone through extensive changes in its climates, geology, hydrology and drainage systems over the past 10 mya; these processes have been postulated as key drivers of diversification. Contrary to the trend where species once broadly distributed are subdivided into several species with restricted distributions, many taxa span the Amazon basin without noticeable genetic differentiation. In my thesis, I studied the phylogenetic and phylogeographic patterns of three widely distributed Amazonian poison frogs: Ameerega hahneli, Ameerega trivittata and Ranitomeya variabilis. I examined phylogenetic relationships based on two different types of genomic data—nuclear and mitochondrial—and I carried out population structure analyses. I investigated the historical biogeography of these species to determine how they have colonized the Amazon Basin over time. Comparative analyses of these three widespread species uncovered complex evolutionary and biogeographic histories. The ancestral distribution of each lineage was in western Amazonia. All three lineages also possess two deeply diverging clades, with one of the clades having a relatively restricted distribution, which seems to be a coincidence rather than the result of a single biogeographic phenomena. In all three species, vicariant events appear to have played important roles, but the vicariant mechanisms varied among taxa. Dispersion across western and into eastern Amazonia was likely affected by the dynamics of the Amazonia during the late Pliocene and Pleistocene, including the altering of hydrological and drainage patterns caused by uplift of the Andes. However, each species seems to be differently affected due to differences in behavior and reproductive ecology. Two species show some evidence of ‘rafting’, a surprising finding that needs to be further investigated. My phylogenetic results revealed a deeply divergent lineage in A. hahneli that needs to be evaluated as a potential species. Comprehensive evaluation of the R. variabilis-amazonica species complex suggests that these taxa came into extensive historical contact and introgressed extensively. Discordances between the mtDNA and nDNA demonstrate the need to perform analysis on both types of data before making taxonomic conclusions and biogeographic inferences. The inclusion of both dramatically improved our understanding of the spatiotemporal patterns of genetic diversity, particularly for widespread species with mixed signatures of historical contact and recent secondary contact.
Access
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