Topographically complex islands present opportunities for in situ (within-island) allopatric speciation because of increased chances for isolation in separate mountain ranges, as well as greater opportunity for fragmentation by high sea levels and climate-driven changes in habitat distribution. Climatic oscillations of the Quaternary (Pleistocene - Holocene; ~2.5 million years ago to the present) may have influenced the severity of vicariant barriers among and within islands, yet how these events influenced evolution of tropical insular biota is not well understood. This dissertation explores the role of topographic complexity and climate-driven range shifts resulting from sea-level changes and habitat suitability in shaping genetic diversity of two Eleutherodactylus frogs (Anura: Eleutherodactylidae) in the Puerto Rican Bank, an archipelago in the eastern Caribbean Sea. Sea level changes significantly altered the size, area, and degree of isolation of terrestrial habitats in the Puerto Rican Bank, and habitat shifts may have occurred in the main island of Puerto Rico. Whereas the Mountain Coquí, E. portoricensis, is restricted to cool and moist understory montane forest habitat in Puerto Rico, the Red-eyed Coquí, E. antillensis, is a habitat generalist with a broad elevational distribution on most of the larger islands of the Puerto Rican Bank. Hypotheses of population history were formulated using data from paleoenvironmental records and ecological niche models, and tested using a suite of population genetic, phylogenetic, and coalescent analyses of DNA sequence data. I show how basin barriers and Quaternary climatic fluctuations shaped the distribution of genetic diversity in E. portoricensis in the Luquillo and Cayey Mountains in eastern Puerto Rico, and how varying degrees of terrestrial connectivity and isolation influenced the persistence and colonization dynamics of E. antillensis across the Puerto Rican Bank. To infer whether climate-driven, historical shifts in distributions occurred in E. portoricensis and E. antillensis, this dissertation also compares patterns of genetic isolation and demography of these species in Puerto Rico, where elevational gradients may have accommodated range shifts during climatic extremes of the Quaternary. The collective findings of this dissertation improve our understanding of topographic and historic factors that promote population divergence and that ultimately produce regional patterns of biodiversity in tropical archipelagos.
Caribbean Sea, climate change, Eleutherodactylus, gene flow, phylogeography, Puerto Rican Bank
Level of Degree
UNM Biology Department
First Committee Member (Chair)
Second Committee Member
Barker, Brittany. "Historical and topographic drivers of tropical insular diversity: comparative phylogeography of Eleutherodactylus antillensis and E. portoricensis, two ecologically distinctive frogs of the Puerto Rican Bank." (2012). https://digitalrepository.unm.edu/biol_etds/3