Temporal changes in allelic variation among Cape Dwarf Chameleons, Bradypodion pumilum, inhabiting a transformed, semi-urban wetland

Abstract

The Cape Dwarf Chameleon, Bradypodion pumilum, is threatened by extensive habitat loss and transformation in the Western Cape Province of South Africa. As a result, the species exists as a collection of populations inhabiting an increasingly fragmented landscape within a critically endangered ecosystem. In this study we monitored microsatellite genetic variation in one of these populations of B. pumilum across a three-year period. From the results of a temporary site-vacancy of adult chameleons during the study, we anticipated a significant shift in microsatellite allele frequencies. Using data from eight highly polymorphic loci we detected differences in the allelic composition of chameleons inhabiting the study site between pre- and post-site-vacancy periods (AMOVA RST = 0.017; P = 0.019). Results suggest that recolonisation by immigrant chameleons, from an adjacent vegetation fragment connected to the study site by corridors, caused the recorded shifts in allelic frequencies. Pairwise tests of year by year comparisons revealed significant shifts in allelic frequencies between years one and two and between one and three, but not between years two and three. Our findings highlight the susceptibility of small vertebrates to stochastic changes in the allelic composition of populations in a fragmented landscape, and can be useful for the development of biodiversity management in an increasingly fragmented habitat mosaic.