DISSERTATION RESEARCH: Evaluating likelihood-based fossil-calibraition methods and timing of repeated incercontinental dispersal in a fossil-rich clade of Boraginaceae

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Fossils are routinely used as the most defensible method for calibrating phylogenetic hypotheses to absolute time. Calibration is often required before ideas can be tested, such as timing of a prehistoric event or rate of change of a trait. This project examines a fossil rich plant group, the Cryptanthinae (Boraginaceae), to test two recently proposed but untested methods for incorporating fossils in phylogenetic analyses. After evaluating these methods, the resulting time-calibrated hypothesis of phylogenetic relationships will be used to examine the New World amphitropical disjunction, a distribution pattern seen in the Cryptanthinae and many other groups of plants that is likely the result of long-distance dispersal by birds between North and South America. This project will result in three main contributions to science. First, evaluation of novel methods for incorporating fossil data into phylogenetic studies will benefit all future studies using fossil data. Importantly, these methods can be generalized to any study using morphological data. Second, New World amphitropical disjunction is common yet understudied. This study will test current hypotheses regarding this biogeographic pattern. Finally, this project will generate a hypothesis of relationships in the Cryptanthinae that will inform taxonomy and conservation in this large and ecologically important plant group.