My research program aims to elucidate how biological diversity is generated and maintained, with a special focus on understanding the link between mating signal diversification and the evolution of premating reproductive isolation. Divergence in mating signals has been shown to drive speciation yet the underlying genetic changes and ecological mechanisms causing this divergence remain little understood. To address this topic, we use a diverse set of taxa and an integrative approach, which includes molecular phylogenetics, evolutionary genetics, population genetics, microbiology, and behavioral and sensory ecology. Below are several projects that forms the foci of research by my lab group.

Because islands are characterized by rich patterns of endemism and striking intraspecific variation, island systems have featured prominently in our understanding of many evolutionary and ecological processes. Populations of the Monarcha castaneiventris flycatcher have diverged in song, plumage color, and extent of sexual dichromatism throughout the Solomon Islands (see header above). The nominate subspecies has a chestnut belly and iridescent blue-black upper parts, and is sexually monochromatic. Two other subspecies have either a white crest or white lores, and both are sexually dichromatic. Finally, a fourth subspecies is completely iridescent blue-black and, like the nominate form, is sexually monochromatic. Using this classic case of island speciation (Mayr 1942), we are attempting to understand the genetic and ecological factors that drive color and song diversification, and how these changes, in turn, contribute to premating isolation.

In addition to geographic variation among islands, hybrid zones, which are regions where genetically distinct taxa meet and produce hybrids, offer unique opportunities to understand speciation and the consequences of signal diversification. The white-collared (Manacus candei) and golden-collared (M. vitellinus) manakins form a hybrid zone (see image below), characterized by several concordant genetic and morphometric clines, centered in Western Panama. The cline for plumage color, however, is displaced over 50 km into the white population, indicating that the golden plumage is moving into the white population. Our work indicates that the dynamics of this introgression is mediated by sexual selection favoring golden males at the hybrid zone (Stein & Uy 2006), and variable habitats favoring golden plumage at the golden population and the hybrid zone, and white plumage at the white population (Uy & Stein 2007).

Intraspecific, genetic polymorphism provides unique opportunities to understand the origin and maintenance of trait diversity within populations. The live-bearing fish Poecilia parae is unique in having five, sympatric male color forms (see image below): two forms that have carotenoid coloration (red & yellow), one form that has structural coloration (blue), one form with vertical stripes and an elaborate dorsal fin, and a final form that lacks the elaborate traits and resembles females. Using a combination of field and lab experiments, our aim is to understand the persistence of this Y-linked polymorphism. We are currently testing the interaction of several factors including: 1) natural selection against colorful males by cichlid predators, 2) premating sexual selection favoring colorful males, 3) postmating sexual selection favoring cryptic males, and 4) variable visual conditions and sensory physiology selecting for variable male coloration.