Mathematical Biology Seminar Scott Nuismer, University of Idaho Wednesday April 8, 2009 3:05pm LCB 215 Predicting correlations between traits of coevolving species Abstract: "Thus I can understand how a flower and a bee might slowly become, either simultaneously or one after the other, modified and adapted to each other in the most perfect manner, by the continued preservation of all the individuals which presented slight deviations of structure mutually favourable to each other." - Charles Darwin, The Origin of Species Since the time Darwin sketched this outline for a process of reciprocal adaptation between a plant and its pollinator, numerous studies have focused on identifying such a coevolutionary process in natural populations. Classic examples include studies of phenotype matching between pollinator and floral morphology, and studies of character displacement in competitors. In these examples, positive correlations between pollinator and floral traits or negative correlations between the traits of competitors are commonly taken as evidence for reciprocal adaptation or coevolution. More recently, similar techniques have been applied to host- parasite and predator-prey interactions as a method for inferring the existence of a coevolutionary process. Although these studies of correlations between traits of interacting species capitalize on data which is relatively easy to collect, it is unclear whether the results can be used to robustly infer the underlying process. In order to shed light on this issue, we developed mathematical models and computer simulations that predict the value of the correlation expected to evolve under ecological scenarios ranging from pure genetic drift to intense coevolutionary selection in populations connected by varying levels of migration. By allowing the distributions of correlation coefficients generated by different ecological scenarios to be compared, these models allow us to determine what we can - and cannot - infer from studies of trait matching in interacting species.