Explaining the biological diversity in tropical America: a phylogenetic and biogeographic approach

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Harboring approximately 37% of the world's species, tropical America is the most species rich region on earth. Understanding the history of such diversity has important implications for species conservation. My long-term research program aims to explain how historical events related to the geography of tropical America have influenced the evolution and distribution of this high species diversity. I will use land plants to address three short-term objectives. *First, I will use DNA from approximately 10 genes to create a phylogenetic tree of the palm group Euterpeae. This tree will permit a reconstruction of the potential geographic regions and habitat types where the ancestors of this group first grew. This reconstruction will test numerous scientific hypotheses. For example, the role of white sands as the ancestral habitat of tropical American plants will be elucidated. Two Msc students will develop this objective aided by undergraduate students in the laboratory. Phylogenetic trees of economically important plants such as palms, and their wild relatives, are important not only for plant classification, but also for crop and horticultural scientists by providing an evolutionary framework to discover important agronomic characteristics.*For my second short-term objective, I will infer the timing of origin and migration of different lineages among the Caribbean islands and the American continent. I will use plant groups for which there is at least 75% phylogenetic information publicly available on the web to extend the sampling from my previous studies. By synthesizing this information, several hypotheses will be tested, for example whether a land bridge facilitated the immigration of plants from the continent to the Greater Antilles, approximately 34 million of years ago. A PhD student will lead this work, and undergraduate students will help to collect information on plant distributions, DNA sequences, and fossils necessary to calibrate the phylogenetic trees. This objective will not only advance the field of biogeography but also the conservation of tropical ecosystems. A comprehensive understanding of past biotic interchange will aid the design of protected and restored areas by considering the local and migration events that led to the current species distribution patterns.*My third short-term objective is to look for evidence of the most common geographic distribution pattern of sister populations undergoing the process of speciation. Populations can become different species even if growing side by side on the same region and exchanging genes during the initial stages (sympatric speciation). An alternative scenario to sympatric speciation is the one in which populations do not have contact because they are separated usually by a geographic barrier, and thus no gene flow occurs between them (allopatric speciation). We will reveal the relative frequency in which these speciation mechanisms occur in tropical America by analyzing the geographic overlap of sister species and its relationship with phylogenetic distance. A second PhD student aided by undergraduates will conduct this objective searching in public databases for plant groups for which there is an almost complete phylogenetic tree (90% information). The outcomes of this objective will be of interest to evolutionary biologists because the spatial and genetic context of current species can provide insight into the nature and strength of the processes leading to speciation. *An understanding of the geographical and genetic factors affecting species origins and distribution in the tropics is also important to explain Canadian species distribution because they all share global climatic and biogeochemical cycles.