The unifying theme of my research centers on understanding the evolution of bizarre, ornamented traits that occur in many species of animals. There are numerous, common examples of these traits: bright coloration of male birds or the huge tails of male peacocks. Sometimes these features appear so exaggerated and huge that they may impede survival, for example, by making individuals more vulnerable to predators. Darwin first recognized the paradox of these exaggerated traits. Even though they may reduce an individual's lifespan, individuals with these traits did reproduce and pass these exaggerated traits on to their offspring in future generations. Darwin proposed that these ornamented traits might function to help in competition for mates. For examples, males might physically compete with other males for access to mates or alternatively, males could compete in attractiveness if females preferred to mate with males that displayed bizarre characteristics. Since Darwin's proposals, biologists have provided strong evidence that males do compete with other males using these flashy characteristics and also that females will preferentially mate with males that have exaggerated traits.
For my dissertation work, I studied Northern Cardinals in upstate New York where I went to graduate school. Cardinals occur throughout the eastern United States and are year round residents. In the breeding season, a male and female will defend a very large breeding territory (1 hectare) and raise young together. Nest predation rates are extremely high, and cardinals build nests and lay replacement clutches throughout the summer. Even if they successfully raise a clutch of young, a pair will attempt to raise multiple broods. In New York, some pairs are able to successfully produce three clutches of young, an impressive feat since it takes more than 30 days to raise a single clutch of offspring. During the winter, males and females form loose, temporary flocks and wander over an area maybe 3-5 times bigger than a breeding territory. For my research I was interested in understanding whether males obtained benefits from displaying bright red coloration, since being so brightly colored might make males more visible to predators. I found that there are benefits associated with having redder plumage. Redder males obtained higher quality territories. These were territories that had really dense vegetation which probably made it more difficult for nest predators to locate nests. Redder males also paired with females that started nesting earlier in the breeding season. In birds early nesting females produce more offspring, maybe because they are older, experienced individuals or because they are in better nutritional condition. In cardinals, early nesting also results in a longer breeding season since pairs are continually attempting to produce offspring during the summer.
As a postdoctoral fellow at Maryland, I continue my interest in the evolution of sexually selected traits and am collaborating with Jerry Wilkinson. In contrast to the field study I did as a graduate student, I am working on understanding how genes controlling these traits evolve and persist. Theoretical work suggests that the genes for these traits may be more likely to evolve/persist if they arise on the sex chromosomes. Stalk-eyed flies are an ideal system to test this theoretical work. Male and female stalk eyed flies have their eyes literally at then ends of stalk, but eye span length is much larger in males than in females for some species. Previous work has shown that males compete for access to females and that males with greater eye span are better competitors; similarly females also choose mates on the basis of eye span and prefer males with greater eye span.
To see publications and more general information about my background, you can look at a copy of my curriculum vitae.
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