The ABCs of Dispersal: Developing an Approximate Bayesian Computation Approach for Estimating Migration Rates from the Distribution of Related Individuals

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Estimating rates of movements of individual animals among populations and habitats is a critical issue in conservation biology, necessary for identifying high quality habitats and determining if declining populations can be rescued by immigration from other populations. The goal of this project is to develop a novel statistical and genetic framework that would improve estimation of dispersal rates for organisms among populations or habitats. The proposed approach involves translating the spatial distribution of related individuals identified with genetic methods into estimates of migration rates. If, for example, a parent and its offspring occur in two different populations or habitats, a movement event must have occurred. This new methodology will be tested through a study of the movements and demographics of Hoffmann's two-toed sloths and brown-throated three-toed sloths living in a shade-grown agricultural ecosystem in Costa Rica. Several hundred individuals of both species will be captured in shade-grown cacao, intact forest, and cattle pastures; males will be radio-tagged and females will be color-marked in order to estimate birth and death rates in the three habitat types. Small tissue samples will be collected for genetic analyses that will provide information about relatively distantly related individuals and precise estimates of movement rates. Patterns of relatedness among the three habitat types will be used to determine the magnitude and direction of movements, and ultimately determine the value of shade-grown agriculture to these sensitive and charismatic tropical mammals. Shade-grown agriculture is increasingly pointed to as a means for protecting tropical biodiversity, but detailed ecological studies of the benefits of such agricultural practices to sensitive species have not been conducted. Because of their sedentary and obligate arboreal life style, sloths are a useful umbrella species for conservation efforts; if shade-grown agriculture can maintain viable sloth populations within fragmented landscapes then agricultural practices could benefit a range of additional tropical species. The statistical and genetic approach developed in this project will be applicable to a range of species and will be made publically accessible via a freely downloadable software package. This project will strengthen research and training collaborations with Costa Rican researchers and will provide research training and mentoring for two postdoctoral scholars.