A grant has been awarded to the State university of New York at Stony Brook under the direction of Dr. R. Geeta to study the relationship of climate to the evolution of herbaceous plants. The grant will improve the doctoral dissertation research of Ramona Walls. This research addresses questions about trait and species diversification by integrating techniques from phylogenetics, species distribution modeling and plant anatomy and physiology. It is designed to test the hypothesis that natural selection by regional climate factors is responsible for the diversification of leaf forms in Mexican Dioscorea, a widespread group of herbaceous vines. Additional species will be sampled to provide a more accurate hypothesis of evolutionary relationships within the genus. This information with be combined with species locality data and physiological measurements from a common garden study to examine form-function relationships in the context of climate tolerances and evolutionary history. Indicators of two leaf functions. water use efficiency and leaf hydraulic conductance, will be measured in a large number of plants in their natural environment. This will make it possible to test the additional hypotheses that the conservatism or evolution of precipitation niches in Mexican Dioscorea is accompanied by the conservatism or evolution of leaf functions, and that the conservatism or evolution of leaf functions is linked to specific sets of leaf traits.
The broader impacts of this research include both social and educational benefits. Mexican Dioscorea contain the wild relatives of a major tropical food crop (yams) as well as many species that are harvested for pharmaceutical compounds. Understanding the evolutionary relationships in this group, and the impacts of climate on its variation and distribution, is therefore economically and socially important. This research is generating a large data-base of plant localities, phenotypic characteristics, environmental tolerances, botanical images and DNA sequences that will be available to the scientific community through publication in online databases. International collaboration is an integral part of this research, and several trips to Mexico have lead to extensive interactions with Mexican scientists and students. Finally, more than fifteen undergraduate students have participated in this research, most from underrepresented groups.
