RAPID: Interacting effects of disturbances on population demography

North Carolina State University, Raleigh NC

Investigators

Abstract

Hurricane disturbances may have large negative impacts on wildlife restricted to small coastal islands, through intense rain, wind, and storm surge. Paradoxically, hurricane disturbance may also regenerate certain habitats that particular species of wildlife depend on. The goal of this research is to investigate the interaction of a periodic, small scale disturbances such as fire, with an extreme disturbance (hurricane) on population growth and survival of an endangered butterfly species, Bartram's scrub-hairstreak (Strymon acis bartrami) and its rare host, pineland croton (Croton linearis). These species are patchily distributed throughout South Florida in rockland habitat, which was recently struck by the eyewall of Hurricane Irma. Results from this research will inform management of fourteen sensitive plants and animals in South Florida, including three additional endangered butterfly species affected by Hurricane Irma. By understanding the mechanisms of how one endangered insect-plant host pair responds to interacting disturbances, this project will provide insight into how these disturbances might influence other sensitive species. This project will also provide research training for a postdoctoral fellow and for undergraduate students. This project will test the hypothesis that hurricanes interact synergistically with more regular, localized disturbances to accelerate habitat change. Based on existing data from an ongoing experiment and observational data on the distribution of the study organisms in relation to previous hurricane disturbances, researchers will test the hypothesis that the two types of disturbances will interact synergistically to increase host plant recruitment and mortality. Prior research has already measured vital rate responses to management-based disturbance (understory removal to simulate wildfire), and this RAPID project will measure vital rate responses to hurricane disturbance and the interaction between management and hurricane disturbances. Empirical data will be used to parameterize demographic matrix models to predict population responses to future interacting disturbances, and to project populations across a range of disturbance frequencies, including frequencies of human-managed disturbances that can be controlled and frequencies of intense hurricanes that cannot be controlled.