GENETIC STRUCTURING SHOWS EVIDENCE FOR PAST BOTTLENECK AND CURRENT DISPERSAL IN A SKY ISLAND ENDEMIC
Sky islands, defined as mountain habitats physically isolated from one another, represent a unique system for studying dispersal in seemingly isolated populations. The Cape Fold Belt of southwest South Africa forms a sky island archipelago of high-altitude alpine Fynbos patches to which the Cape Rockjumper Chaetops frenatus is an avian-endemic. Continued contraction of habitat due to increasing temperatures may be causing further isolation of C. frenatus populations beyond their capability for efficient dispersal. In this study I investigated genetic structuring in C. frenatus by collecting 71 blood samples from 13 localities representing eight mountain ranges and isolating two mitochondrial markers and one nuclear marker (1340 bp in total) using Analysis of Molecular Variance (AMOVA), and Bayesian and maximum likelihood inference. I found low overall genetic diversity within C. frenatus, however, I also found no evidence for geographically-based genetic structuring among populations of C. frenatus, or for inbreeding within localities. Haplotype networks suggest C. frenatus may have experienced a bottleneck or founder effect in their recent genetic past, a result supported by a significantly negative Tajima's D. A bottleneck of C. frenatus may have occurred from glacial refugia in the Cape Fold Belt, or C. frenatus may have evolved from a founder population of nearby (and genetically similar) sister-species –– C. aurantius.  As the first avian genetic structuring study to arise from the Cape Fold Belt sky islands, my results show no evidence that C. frenatus are unable to disperse across inhospitable lowland habitat, and thus may not experience isolation due to climate change.