Mating system and intrapatch mobility delay inbreeding in fragmented populations of a gecko

Abstract

Habitat fragmentation can cause high levels of inbreeding within populations by creating small isolated populations and therefore can affect population survival. While most genetic studies of fragmented systems focus on the impact of habitat fragmentation on interpatch patterns or processes, here we focus on inbreeding (avoidance) processes within patches. We used both genetic and mark-recapture data to study within-patch processes in fragmented and continuous populations of the gecko Oedura reticulata in the Western Australian Wheatbelt. Our results revealed that O. reticulata in fragments and continuous populations alike share a promiscuous mating system (involving both polygyny and polyandry) and exhibit no detectable difference in mean levels of relatedness. However, we also found that proportions of full- and half-sib matings were higher in the habitat fragments, subadults disperse further, and all demographic classes move further and more frequently. We contend that the net result of this combination of promiscuity and greater movement is that small isolated populations have been able to retain mean levels of relatedness similar to those in nearby continuous habitat despite fragmentation and close to complete isolation over generations. It is likely that these behavioral changes have ameliorated some of the genetic effects caused by habitat fragmentation, potentially delaying reductions in the fitness effects expected from fragmentation into small populations.