Individual fitness, directional dispersal, and the dynamics of trailing-edge populations

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

Biodiversity conservation is one of the great challenges of the 21st century, and conservation efforts depend on information about how environmental change will impact wildlife. For many species, it is unclear whether population declines are the result of reduced reproduction and survival, or if local populations are shifting as individuals move in search of better environmental conditions. Reduced reproduction and survival would negatively affect genetic diversity and increase extinction risk, whereas movement towards preferred habitat could allow species to avoid negative impacts of environmental change. This research will develop a new framework for using data from field studies to determine the contributions of reproduction, survival, and movement to changes in species distributions. The new framework will be applied to long-term data collected on bird populations in the southern Appalachian Mountains where numerous species are restricted to high elevations and are sensitive to recent changes in temperature and precipitation. Results will advance knowledge about population dynamics and extinction risk while enhancing society's ability to prioritize species and regions in need of conservation. Quantifying fitness in natural populations is notoriously difficult because survival and reproductive rates can vary greatly among individuals as a result of spatial variation in the environment and heterogeneous phenotypic traits. For animals, the problem is complicated by location-dependent survival and reproductive rates that can change continuously in time as individuals move through complex landscapes. This project will develop theory and methods needed to understand spatial, temporal, and individual-level heterogeneity in fitness of mobile organisms, even when demographic data are incomplete and subject to observation error. The new framework will be used to determine if trailing-edge populations of birds at the southern edge of their geographic range will experience fitness reductions in response to climate change, or if populations can preserve fitness via directional dispersal towards cooler climates. Mark-recapture data, count data, and nest monitoring data will provide information about spatio-temporal variation in reproduction, survival, and species distribution over a pronounced elevation-driven climate gradient. Information about the effects of environmental change on dispersal distance and directionality will be collected using novel tracking technologies that yield precise location information for small songbirds. 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.