Habitat fragmentation promotes fluctuating asymmetry but not morphological divergence in two geckos

Abstract

The process of species formation is often ignored in discussions on the conservation of biodiversity. Yet the clearance of vegetation may promote divergence among populations of a species through isolation, providing conditions for rapid genetic drift and novel selection pressures. Here, stepwise discriminant function analysis and fluctuating asymmetry are used to examine variation in morphology within and among non fragmented and recently fragmented populations of two species of gecko,Oedura reticulata andGehyra variegata. High reclassification error rates using discriminant function analysis, indicate that fragmentation has had no detectable effect on morphological differentiation among populations of either species. In contrast, remnant populations of both species exhibit higher mean levels of fluctuating asymmetry than do populations in undisturbed habitat. ForOedura reticulata, levels of fluctuating asymmetry are negatively correlated with the log of adult population size. These results suggest that the changes following habitat clearance have been severe enough to cause increased developmental instability in populations of both species but not detectable morphological divergence. Given the high rate of extirpation of gecko populations in the study region and the extreme vulnerability of the remaining populations, it is unlikely that species formation will be significant in maintaining reptile diversity in that region.