Projects

My doctoral research develops phylogenetic, population genetic, and theoretical approaches to investigate the evolutionary consequences of ecological species interactions. Here's a brief look at what I'm up to right now.

Species interactions and evolutionary diversification

Ever since Darwin, evolutionary ecologists have believed that species interactions contribute significantly to evolutionary diversification, and a growing body of phylogenetic, ecological, and theoretical evidence has given strong support to this idea. One issue that remains unresolved, however, is the question of how different kinds of ecological interactions may differ in their promotion of divergence in interacting species. Many comparative studies support an association between a wide variety of species interactions and increased diversity; but theoretical and empirical results on finer scales are less clear-cut. Meanwhile, theories of adaptive radiation, including Simpson's and Schluter's, have emphasized competition among ecological competitors as the major driver of diversification, and treat interactions between trophic levels as venues for competition rather than sources of diversification.

To help answer these questions, I have developed a mathematical model and individual-based simulations of coevolution between two species interacting in different ways (as mutualists, as host and parasite, as competitors, &c.), in order to compare a common measure of evolutionary divergence arising from each type of ecological interaction. I have also reconstructed the evolutionary history of yucca moths to determine the ecological conditions that preceeded the origins of the yucca-yucca moth mutualism and examined genetic divergence in non-pollinating yucca moths.

Relevant publications

Yoder JB and SL Nuismer. "When does coevolution promote diversification?" Accepted pending minor revision at The American Naturalist.

Yoder JB, E Clancey, S Des Roches, JM Eastman, L Gentry, WKW Godsoe, T Hagey, D Jochimsen, BP Oswald, J Robertson, BAJ Sarver, JJ Schenk, S Spear, and LJ Harmon. 2010. "Ecological opportunity and the origin of adaptive radiations." Online in advance of publication at the Journal of Evolutionary Biology 23(8):1581-96. Full text (Open access).

Yoder JB, CI Smith, and O Pellmyr. "How to become a yucca moth: Minimal trait evolution needed to establish the obligate pollination mutualism." Biological Journal of the Linnean Society 100(4):847-55. Abstract. Full text (PDF, 656KB). Supplementary material (PDF, 217KB).

Drummond CS, H-J Xue, JB Yoder, and O Pellmyr. 2010. "Evidence for host-associated divergence and incipient speciation in the yucca moth Prodoxus coloradensis (Lepidoptera: Prodoxidae) on three parapatric host plants." Heredity. 105(2):183-96 Abstract. Full text (PDF, 907KB).*

Coevolution and divergence in Joshua tree

The largest portion of my dissertation will be concerned with the Pellmyr Lab's current focus: the co-divergence of Joshua tree, Yucca brevifolia, and its pollinators, the yucca moth species Tegeticula synthetica and T. antithetica. The parapatric distributions of these two pollinators correspond exactly to the distributions of two previously- recognized varieties of Joshua tree. These two varieties differ significantly in many ways, but the strongest divergence is seen in traits directly related to the yucca moth-Joshua tree interaction.

What remains to be seen is whether the morphological divergence in Joshua tree and its pollinators is borne out in the distribution of genetic diversity within the species, and whether the specific nature of the pollination interaction has shaped the spatial scale of this divergence. To help answer these questions, I am presently working to develop informative nuclear markers for phylogeographic and population genetic analysis of Joshua tree populations.

Relevant publications

W Godsoe, JB Yoder, CI Smith, CS Drummond, O Pellmyr. "Absence of phenotype matching in an obligate pollination mutualism." In review for the Journal of Evolutionary Biology.

Smith CI, CS Drummond, WKW Godsoe, JB Yoder, and O Pellmyr. 2009. "Host specificity and reproductive success of yucca moths (Tegeticula spp. Lepidoptera: Prodoxidae) mirror patterns of gene flow between host plant varieties of Joshua tree (Yucca brevifolia: Agavaceae)" Molecular Ecology. 18(24):5218-29. Abstract. Full text (PDF, 456KB).

Godsoe WK, E Strand, T Esque, CI Smith, JB Yoder, and O Pelmyr. 2009. "Divergence in an obligate mutualism is not explained by divergent climatic factors." New Phytologist 183(3):589-99. Abstract. Full text (PDF, 3.7MB).

Smith CI, WKW Godsoe, S Tank, JB Yoder, and O Pellmyr. 2008. "Distinguishing coevolution from covicariance in an obligate pollination mutualism: Asynchronous divergence in Joshua tree and its pollinators." Evolution 62(10):2672-87. Abstract. Full text (PDF).

Godsoe W, JB Yoder, CI Smith, and O Pellmyr. 2008. "Coevolution and divergence in the Joshua tree/yucca moth mutualism." The American Naturalist 171(6):816-23. Abstract. Full text (PDF).