Numerous plant groups?approximately 330 families and 60 genera?have distribution patterns spanning the tropical regions of South America, Africa, and Australasia. These complex modern distribution patterns suggest a dynamic history for tropical ecosystems, involving frequent biotic exchange among major tropical regions over geologic history. Detailed evolutionary studies of widespread tropical groups can shed considerable light on the historical factors that have shaped the global distribution patterns of tropical organisms and ecosystems. However, such studies require extensive fossil evidence to reveal the timing and location of diversification events, and the fossil record of tropical plants is notoriously poor. The Icacinaceae, a pantropical family of flowering plants including approximately 140 species of woody vines and trees, are unique among tropical groups in that they have an excellent fossil record, documenting a diversity of genera across wide geographic and geologic ranges. This makes the Icacinaceae an excellent model for inferring broader historical patterns of tropical plant expansion and diversification across the tropics. This project will integrate the extensive fossil record of Icacinaceae with DNA-based studies of relationships among species in the family. The result will be a comprehensive picture of the family?s evolutionary history, offering important broader implications for tropical plant diversification and spread in response to climatic and geologic changes over the past ~65 million years. Additionally, this study will resolve the precise evolutionary placement of Icacinaceae in the flowering plant tree of life, which has been ambiguous in previous studies.
This project will integrate cutting-edge DNA sequencing techniques with traditional morphological and paleobotanical approaches, providing a diversity of training opportunities for graduate, undergraduate, and high school students. The synthetic approach employed here will also serve as a methodological model for future studies aiming to combine DNA and fossil evidence for reconstructions of historical biogeography. The results of this research, which will be disseminated at meetings and in peer-reviewed publications, will be of interest to both tropical biologists and angiosperm systematists given the broader importance of Icacinaceae for understanding both tropical biogeography and patterns of morphological evolution across the flowering plant tree of life.
