RICHMOND, Jonathan; Univ. of Connecticut: A case for parallel speciation in North American Scincid Lizards

Parallel speciation is a special case of homoplasy where traits determining mating compatibility evolve repeatedly in separate lineages experiencing similar environments. The outcome of such parallel evolution is that ecologically divergent but closely related populations show higher levels of reproductive incompatibility than ecologically similar but distantly related ones. I am currently studying a candidate example of parallel speciation in skinks of the Eumeces skiltonianus species complex. This complex is composed of two ecomorphs that differ in body size, coloration, and ecology. Phylogenetic analysis provides strong evidence that a larger, arid adapted ecomorph (i.e. gilberti) has evolved 3 times from within a smaller, mesic adapted ecomorph (i.e. skiltonianus). Disruptive selection appears to have facilitated the divergence, with body size serving as the target of selection. Indirect evidence suggests that two of the gilberti clades are merging as a consequence of secondary contact, indicating that speciation has occurred through parallel processes. However, to demonstrate parallel speciation, independently derived lineages of the same ecomorph must be shown to be reproductively compatible. Here, I present the results of mate choice experiments to evaluate the contribution of 3 predictor variables (genetic distance, geographic distance, and body size) on the probability of copulation success. I use logistic regression in a Bayesian framework to show that body size is the primary determinant of reproductive compatibility and that geographic and genetic distance has insignificant effects on copulation success. These data support the case for parallel speciation and lend insight into the ways in which ecology promotes speciation.