Research Interests

My research integrates behavior, ecology, and evolution, focusing on sexual dimorphism and plant-pollinator interactions. These two topics seem quite different, yet they nonetheless share a common goal, which is to understand how ecological processes such as competition and mutualism shape patterns of morphology in plants, and patterns of morphology and behavior in animals. Since 1999, I have been studying sexual dimorphism in the purple-throated carib (Eulampis jugularis), a hummingbird native to the Lesser Antilles of the Caribbean. Although the wings and body masses of males average 8.6% and 25% larger than those of females, the bills of females average 30% longer than those of males, one of the most extreme bill dimorphisms of any hummingbird. Moreover, the curvature of female bills is 50% greater than the curvature of male bills. In studies on St. Lucia and Dominica, my students and I determined that this hummingbird is the sole pollinator of Heliconia caribaea and H. bihai, with flowers of the former corresponding to the short, straight bills of males, the larger sex, and flowers of the latter to the long, curved bills of females. On St. Lucia, we found that H. bihai has a second color morph with flowers matching the bills of males, whereas on Dominica, H. caribaea has a second color morph with flowers matching the bills of females. In addition, on both islands the heliconias vary in the number of flowers per inflorescence so that the nectar rewards of all Heliconia morphs are consistent with each sex's choice for the morph corresponding to its bill morphology and energy requirements, supporting the hypothesis that feeding preferences have driven their co-adaptation. Presently, we are studying the relative importance of natural and sexual selection in the maintenance of sexual dimorphism in bill and body size of the hummingbirds, and mechanisms of natural selection in the maintenance of differences in floral traits between the heliconias. Our work has been profiled in Science, Nature, Science News, The Associated Press, The San Francisco Chronicle, Smithsonian Magazine, and The Encyclopedia Britannica Book of the Year (2004, 2001) and is featured in the Partners in Evolution exhibit in the Smithsonian National Museum of Natural History and in PBS-Nature "Hummingbirds: Magic in the Air" (click on title to view).