Adaptive radiation occurs when a single species invades a new environment (for example, an island) and subsequently diversifies into many species, each specialized to thrive in a particular segment of that new environment. Current understanding of adaptive radiation emphasizes the importance of resource scarcity and competition as the engine of diversification; in contrast, the role of predators in promoting or inhibiting such rapid bursts of evolution is largely unknown. This research will lead to better understanding of how competition and predation interact to (a) determine whether closely related species can coexist (a prerequisite for adaptive radiation), and (b) shape the subsequent evolutionary trajectories of those species. This experiment will improve science relevant to invasive-species management, which in in the national interest. This project also involves innovations in STEM education that will strengthen the scientific workforce.
Competition for limiting resources has long been thought to be the primary driver of adaptive radiation, and is the foundation for existing theory, but predation may play an equally important role in mediating species coexistence and diversification within adaptive radiations. This project focuses on the classic Anolis lizard adaptive radiation, using whole-ecosystem manipulations on 16 small Caribbean islands to assess how predation by curly-tailed lizards (Leiocephalus carinatus) affects competitive interactions between an established resident lizard species (Anolis sagrei) and experimentally introduced populations of a more arboreal lizard species (Anolis smaragdinus). Population trends, behavioral responses, diet composition, and genetic and morphological changes of all three lizard populations will be monitored. Molecular diet analysis (including isotopic analyses), radio-telemetry, and genomics (RAD-tag and RADseq sequencing) will be used to quantify variables, which will be tested for interaction and differences using standard and Bayesian statistical methods. Broader impacts include illumination of mechanisms underlying the success or failure of invading populations on islands, and the development of an undergraduate course combining interdisciplinary (including humanities) and field-based approaches.
