Evolution of Life History Traits
Geographic Clutch Size Variation: A Test of Three Hypotheses
For many terrestrial vertebrates, clutch size is positively correlated with latitude, with animals producing more offspring per reproductive attempt at higher latitudes. Three hypotheses have been proposed to explain this global latitudinal clutch size gradient, but the highly mobile nature of most endotherms has confounded previous attempts to identify the causal mechanism(s). This project uses 2 approaches to test the alternative hypotheses for this global pattern: 1) test explicit predictions across species based on >1,000 species of extant snakes, and 2) test those same predications within one species (the western rattlesnake). So far, we have collected clutch size data for more than 100 live and preserved rattlesnakes and compiled a database that contains clutch sizes for ~900 species of snake. These data will be used to 1) quantify the role of intraspecific plasticity in latitudinal clutch size variation 2) identify the mechanisms responsible for intraspecific clutch size variation, and 3) improve our understanding of the risks faced by one of North America's most widespread snakes.
Emily Martin
Evolutionary History and Adaptive Divergence of Burrowing Owls throughout the Americas
Burrowing Owls (Athene cunicularia) occupy a broad geographic distribution, ranging from Canada to Argentina, including Caribbean and Pacific Island populations. Despite this expansive distribution and substantial ecological variation, the evolutionary relationships among populations across the Americas remain poorly understood. For this project, we are reconstructing a comprehensive range-wide phylogeny using whole genome sequencing. The analyses will clarify patterns of divergence, historical connectivity, and colonization history across the species’ range throughout the western hemisphere. By estimating divergence times and patterns of historical gene flow, we aim to provide the first high-resolution evolutionary framework for Burrowing Owls throughout the western hemisphere. We are also investigating adaptive evolution and genomic resilience within the western (A. c. hypugaea) and Florida (A. c. floridana) subspecies. These subspecies differ in behavior, habitat use, population trajectories, and conservation/management status. Using whole genome sequencing, we are testing for signatures of local adaptation, identifying genomic regions associated with environmental gradients and land use, and evaluating differences in genetic diversity and inbreeding. This work will assess the evolutionary potential of isolated extant populations and determine whether adaptive divergence contributes to contemporary demographic patterns.
Matthew Dunning