Abstract for presentation at Biodiversity Extinction Crisis Conference - A Pacific Response

Habitat fragmentation, through its effects on habitat area, quality and connectivity is likely to have major consequences for habitat use, social structure and mating systems. However, these effects, and the role they may play in local extinction, are poorly understood. An important component of mating systems that is potentially affected by habitat fragmentation but rarely addressed in this context is inbreeding avoidance. Dispersal is considered the primary inbreeding avoidance strategy for many species for which restricted dispersal in fragmented habitat thus increases the risk of inbreeding. This may decrease offspring fitness and contribute substantially to the increased extinction risks of patch populations. The alternative to an increased inbreeding rate in fragmented habitat is behavioural avoidance of mating with close relatives, which could occur via the choice of relatively unrelated mates, or the avoidance of mating altogether. For example studies on some northern hemisphere small mammals have shown that reduced patch connectivity and increased inbreeding risk can lead to a reduced reproductive output. In the Australian context we have utilized a genetic marker approach to 1/ identify demographically isolated populations of a small mammal, the agile antechinus (Antechinus agilis) and a much larger one, the southern hairy-nosed wombat (Lasiorhinus latifrons), and 2/ compare social organization with respect to relatedness in isolates, to that in continuous populations. We have thus identified in these species fragmentation-driven perturbations to socioecology, and can speculate on their potential to contribute to extinction of isolated populations. It is hoped that further research in this area will lead to a better understanding of the effects of habitat fragmentation on processes impacting population functioning and persistence. This will enable researchers and managers to better understand and predict the response of ecological communities to habitat fragmentation.