Comparative Phylogeography of 12 Widespread Tropical Rainforest Tree Species

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Tropical rainforests contain the most species-rich plant assemblages on Earth, yet the processes that generate this diversity are poorly understood. The proposed research investigates genetic processes leading to speciation in 12 rainforest tree species found throughout tropical America and, for three species, West Africa. The study is focused on (1) the importance of tropical mountains as barriers to dispersal, (2) effects of regional forest histories on levels of genetic diversity within species, and (3) biotic interchange between Africa and the tropical America. This research will test the contrasting hypotheses that widespread tropical tree species are either genetically cohesive populations or species complexes with high levels of genetic divergence.Tropical forests are under severe pressure from agricultural expansion and climate change. In order to conserve genetic diversity of tropical hardwoods it is essential to understand how genetic diversity is partitioned within and among species. The proposed research highlights the role of geography in shaping the distribution of genetic variation, and it will pinpoint biogeographic centers of genetic variation for important species such as kapok (Ceiba pentandra) and balsa (Ochroma pyramidale). The research involves collaboration with the Smithsonian Tropical Research Institute and Latin American and African institutions.