Although plant adaptations to aridity have been well studied in a few groups, such as cacti, relatively little is known about the diversification of most plants in deserts and other drylands. A group of milkweeds (Matelea subg. Chthamalia) inhabits dry or seasonally dry habitats in Mexico and the southwestern United States, providing a useful system for investigating adaptive diversification in arid bioregions. This group is part of a large, mostly tropical clade of milkweed vines (Gonolobinae) and most exhibit apparent adaptations to aridity. Many have lost their ability to twine (with stems spreading flat on the ground), have small, bell-shaped flowers, or are covered by an abundance of hairs. This research will use the most powerful available techniques to reconstruct the evolutionary history of Chthamalia and to analyze the evolution of adaptations to aridity. Next generation DNA sequencing employing a ?genome skimming? approach will be used to obtain complete chloroplast genomes, partial mitochondrial genomes, and complete nuclear ribosomal gene sequences to robustly estimate phylogenetic relationships, which will serve as a framework for evolutionary analyses of morphological adaptations.
This project will resolve the classification of little-known plants that have been taxonomically controversial. Several species of Chthamalia are exceedingly rare; resolving taxonomic questions and greater knowledge of their evolution will contribute to future conservation efforts of species and habitats. Integration of traditional systematic approaches with new molecular methods is critical to address hypotheses about evolution, adaptation, and speciation. Graduate and undergraduate students will gain laboratory and bioinformatic training as well as the opportunity to present research results at national meetings.