Projects

My goal in graduate school is to develop multiple lines of inquiry investigating the evolutionary consequences of ecological species interactions. Here's a brief look at what I'm up to right now.

Phylogeography and population genetics of 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.

For more information, see

Smith CI, WKW Godsoe, S Tank, JB Yoder, and O Pellmyr. "Distinguishing coevolution from covicariance in an obligate pollination mutualism: Asynchronous divergence in Joshua tree and its pollinators." Accepted (pending minor revision) for Evolution.

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).

Pellmyr O and KA Segraves. 2003. "Pollinator divergence within an obligate mutualism: two yucca moth species (Lepidoptera; Prodoxidae: Tegeticula) on the Joshua tree (Yucca brevifolia; Agavaceae)." Ann. Entomol. Soc. Am. 96:716-22. Full text (PDF).

Modeling species interactions and divergence

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.

To help answer this question, I am developing a mathematical model of divergence in two interacting species, using the "quantitative traits" framework popularized by the work of Russell Lande. The model will simulate coevolution between two species interacting in different ways (as mutualists, as host and parasite, as competitors, &c.) and compare a common measure of evolutionary divergence arising from each type of ecological interaction.

For more information, see

Ehrlich PR and PH Raven. 1964. "Butterflies and plants: a study in coevolution." Evolution 18:586-608.

Farrell BD. 1998. "'Inordinate fondness' explained: Why are there so many beetles?" Science 281:555-9.

Lande R. 1979. "Quantitative genetic analysis of multivariate evolution, applied to brain:body size allometry." Evolution 33:402-16.

Schluter D. 2000. The Ecology of Adaptive Radiation. Oxford Univ. Press.