Dr. James H. Leebens-Mack of Colgate University, in collaboration with Dr. N. Olof Pellmyr at Vanderbilt Univerisity has beeen awarded a grant to study coveolutionary interactions between plants and moths. Coevolution is an important process in driving diversification and speciation, but understanding of this process is hampered by a lack of phylogenies (family trees) for model groups of organisms. Yuccas and yucca moths are tied in an obligate pollination mutualism, commonly cited as one of the most obvious examples of coevolution. The PIs propose to use multi-gene sequencing to complete robust organismal phylogenies for both yuccas (Agavaceae) and yucca moths (Prodoxidae: Lepidoptera). The results will be used to test hypotheses of coevolution, parallel speciation, and the role of host shifts in diversification. Comparative analyses will be used to quantify coevolution at the level of individual traits in the moths and plants.
The goal of objective 1 is to establish a stable phylogeny based on DNA sequence data for the plant genus Yucca. They will use a multi-gene approach, using both nuclear and cytoplasmic markers, to establish a robust species-level phylogeny. In objective 2, the PIs will use a similar approach to resolve relationships among a cluster of rapidly diversified groups of yucca moths whose origin coincided with much life history evolution. Objective 3 utilizes the moth and plant phylogenies to test hypotheses related to coevolution. The distribution and frequency of cospeciation will be estimated, and and comparative analysis emplyed to test how host shifting and evolution of oviposition behavior affect diet breadth and rates of diversification. Finally, the underlying conflict of interests between moth and plant should manifest through selection on traits with major effects on oviposition success in the moth and minimization of seed destruction in the plant. Moth ovipositor shape, oviposition site, and floral ovary shape and thickness are candidate traits that are highly variable among species. They will be the focus of ancestor reconstruction and comparative analyses to partition coevolutionary and phylogenetic components of diversification.
Together, the results from the project should provide the first phylogenetic framework at the species level for any of the models of coevolution and mutualism. It will open a venue for analyzing how coevolution acts at the trait level to contribute to the generation of biodiversity.