Adaptive radiation is the diversification of an ancestral lineage into a multitude of ecologically adapted species. This study will use the West Indian radiation of Sphaerodactylus geckos to investigate two hypotheses emerging from recent work on adaptive radiation: (1) adaptation is replicated among radiations isolated by time or geography, and (2) access to ecological opportunity drives diversification. Sphaerodactylus is an ideal group to test these hypotheses because multiple evolutionarily independent radiations occur across the West Indies. This study will address each hypothesis by combining morphological and habitat-use data with phylogenetic comparative methods and geometric morphometrics, to assess the extent of replicated adaptation and the importance of access to ecological resources in the diversification of Sphaerodactylus.
Throughout this project, undergraduate assistants will be trained in a variety of field, laboratory, and analytical techniques. Results from this study will be disseminated through scholarly journals and conferences, as well as through journals and symposia organized by gecko enthusiasts. Furthermore, results from this study will be incorporated into a pre-collegiate summer program at the University of Rochester, to expose students to both emerging research and applied science. Finally, this study will contribute to the conservation of these poorly known geckos.
How adaptation and speciation contribute to the biodiversity and the distribution of organisms is a central question in biology. This study used a little studied group of geckos from the Caribbean (Sphaerodactylus) to quantify how adaptation and speciation have shaped their physical appearance and where they occur on islands across the archipelago. In the Caribbean, gecko species occur in habitats that range from exceedingly dry, cactus-dominated deserts to cold mountain cloud forests. To understand the changes in gecko shape and size, we generated hundreds of x-ray images from dozens of species, produced hundreds of new natural history specimens, and collected DNA sequence data that will inform the basis of species descriptions and conservation initiatives. The novel methodological framework developed for this study can be used and extended by future researchers, and the data generated during the course of research may also form the basis of future studies. Some of the important findings of this study include the observation that skull shape of these geckos changes predictably with the environmental conditions of a region; species found in hot and dry habitats tend to have blunt snouts whereas species from wet forests typically have elongated, narrow snouts that are reminiscent of a birdâ€™s beak. This correlation is indicative of natural selection directing the evolution of skull shape, and is different from a pattern seen in another better-studied lizard group, the anoles, that also live in the Caribbean where adaptation to locally variable habitat conditions has resulted in morphologically distinctive species. Therefore, this study observed that a similar evolutionary process (adaptation) might result in similar patterns of morphological distinctiveness for different groups of species living in the same area, but does so in response to different aspects of environmental variation (regionally or locally variable conditions). Additionally, there are many gecko species on the island of Hispaniola unknown to science and several unrecognized species await description and perhaps conservation protection as well.