Abstract
Speciation may occur when animals diverge in communication traits that facilitate reproduction, such that animals with divergent signals can no longer recognize each other as mates or strongly prefer mates of their own species. These signals may be received via visual, auditory, or chemosensory means, and may be used in combination as multimodal communication. My dissertation focus is signal divergence and its influence on behavioral isolation. The Reef Gecko (Sphaerodactylus notatus) is a small lizard native to The Bahamas, Cuba, and Florida. Populations of this species have diverged in dichromatic pattern such that the Florida population is variably dichromatic while other populations are clearly dichromatic. To explore the complex biogeographical and evolutionary relationship between these subspecies, I use phylogenetic reconstruction, population genetics, and demographic modeling. I reconstructed evolutionary relationships and approximate time of divergence for these subspecies and used population structure analyses to identify patterns of co-ancestry within populations. By constructing demographic models based on geologic and climate change in the region, I tested for the effects of reproductive isolation and climate fluctuation on gene flow, building a more complete understanding of the history of this species. I then test the hypothesis that levels of sexual dichromatism facilitate sexual recognition in S. notatus. I recorded encounters between same sex and opposite sex pairs of geckos that were separated by a transparent barrier to prevent chemical communication. The Florida mainland population with variable sexual dichromatism was also tested without a transparent barrier, allowing comparison between encounters with and without use of chemical signal. Each encounter was evaluated for courtship or agonism between gecko pairs, allowing me to measure the influence of sexual dichromatism on the recognition of potential mates. In whole, my dissertation explores island diversification from a biogeographical, evolutionary, and behavioral perspective.