Eco-evolutionary dynamics of parasitism mediated through variance in host fitness

Nearly all animals and plants are infected by parasites that can reduce health and performance. In addition to these overall effects, parasites are predicted to increase variation among individual hosts in health and performance. Parasites are therefore predicted to shape the ecology and evolution of the host species. These predictions apply to any plant or animal host-parasite interaction but testing them requires a species in which (1) parasites can be manipulated and (2) health and performance can be measured across the entire lifetime for thousands of individuals. This project uses a custom drug delivery method to remove several different species of parasitic worm from a wild population comprised of thousands of individual lizard hosts. These hosts are short-lived and occur on small islands where the entire population can be accurately censused several times per year. Genetic methods have recently been developed to match parents to offspring each year, so lifetime survival and reproduction can be measured for thousands of individuals, in both de-wormed and untreated treatments. The project will test whether and how parasites influence variation in host health and performance. The results will increase understanding of the ecology and evolution of infectious disease while also testing fundamental evolution theory. The project will impact science education by supporting the professional development of science teachers through summer workshops. The workshops focus on building skills in data collection, analysis, and graphing, and in transmitting those skills to K-12 students. Postdoctoral, graduate, and undergraduate researchers will be mentored in this project, with a focus on undergraduates in the Louis Stokes Alliance for Minority Participation. Although it is well known that parasites reduce the mean fitness of their hosts, few studies have tested whether parasites influence variance in host fitness or explored the resulting evolutionary dynamics for host populations. This is particularly true when considering total lifetime fitness, which is notoriously difficult to measure in most wild populations. This project will combine new high-throughput techniques in ecological molecular genetics (GT-seq) with established approaches in quantitative genetics (animal models) to provide a detailed, multi-generational characterization of total lifetime fitness and its quantitative genetic architecture in a wild population with both experimental and natural variation in parasite burdens. The nature of the dataset will also allow total lifetime fitness to be decomposed into its components (juvenile survival, adult survival, mating success, reproductive success), and for evolutionary dynamics of disease and parasitism to be considered separately for females and males, thus providing additional insight into key evolutionary hypotheses about sex differences in selection and in parasite resistance and tolerance. The Summer Teacher Workshop will be done in collaboration with makers of educational technology that teaches data skills to middle- and high-school students using authentic statistics combined with “ready- to-teach” modules featuring curated real datasets. 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.