Collaborative Research: Inferring the impacts of closely-related species on phenotypic evolution

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In a classic example of natural selection on islands, the remarkable differences among the bills of Darwin’s finches allow these species to co-exist because they eat very different types of food. The same processes may also be important in shaping evolution in many other organisms, but their effects can be difficult to detect without the clear geographic boundaries of islands and the strikingly different body forms of Darwin’s finches. This project focuses on Sceloporus lizards, a large group of species that often co-exist, and that are abundant throughout Mexico and the southwestern United States. The researchers will gather detailed measurements of body shape and environmental features, and develop new statistical approaches to identify body and habitat types distinct from generalist, mainland species. They will then test whether species that co-exist in the same geographic areas differ from each other in body form and ecology, and reconstruct the ancient history of co-existing species with geographic precision. The project emphasizes international collaboration (US and Mexico) and community science practices. It will also embed the research in formal courses taught at three institutions, and disseminate results through museum exhibits and other forms of public outreach. Closely related taxa that live in geographic proximity (i.e., sympatric congeners) impose a potentially widespread and under-recognized evolutionary phenomenon. This project will gather new data from CT scans and from geometric morphometric analyses of museum specimens, conduct lizard field surveys of 500 sites in Mexico and the southwestern United States, and develop new phylogeographic tests of whether Sceloporus lizards tend to co-exist with closely related taxa. In addition, the researchers will combine phylogenetic, climate, and fossil information to reconstruct the detailed evolutionary and geographic history of Sceloporus species assemblages and their morphologies, testing hypotheses about the processes by which interspecies interactions lead to species turnover and diversification. These analyses will test hypotheses about the importance of foraging, habitat use, and parity as drivers of interspecific interactions, ask whether sympatric congeners have imposed similar selective pressures in repeated evolutionary episodes, and test for links between the biodiversity of sympatric species assemblages (e.g., species richness, phylogenetic diversity) and landscape characteristics (e.g., habitat heterogeneity). The project will also contribute to future studies by adding new data and R scripts for those who want to conduct similar analyses with other taxa.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.