Dispersal and population structure of the rufous bettong, Aepyprymnus rufescens (Marsupialia: Potoroidae)

Abstract

Many species of herbivorous mammals declined to extinction following European settlement of inland Australia. The rufous bettong, Aepyprymnus rufescens (a macropodoid marsupial), is ecologically similar to many of these species. We used analysis of microsatellite markers to determine dispersal patterns and mating system characteristics in a cluster of local populations of A. rufescens, with the aim of gaining a better understanding of regional population dynamics in such species. Particularly, we asked whether the rufous bettong showed source-sink dynamics, as Morton (1990) hypothesized that many mammals may have been made vulnerable to extinction through such processes. We compared populations separated by distances of up to 12 km, and detected significant genetic differentiation among local populations (FST = 0.016). Females displayed greater genetic structuring than males, suggesting that females dispersed over shorter distances or less frequently than males. Geographic distance was weakly related to genetic distance between populations suggesting some gene flow at this scale, and paternity assignment indicated that dispersal can occur over distances of up to 6.5 km. Our study populations varied widely in density, but density did not explain the pattern of genetic differentiation observed. These findings of significant structure among populations, some influence of distance on genetic divergence and that density explains little of the divergence among populations, suggested that source-sink dynamics did not play a large role among these populations. Variance in male mating success was low (maximum assigned paternity for an individual male was 14% of offspring). While data on multiple maternity were limited, roughly half of repeat maternity was assigned to the same male, suggesting that the mating system of the rufous bettong is not purely promiscuous.