Genetic variation in morphologically divergent mainland and island populations of Soemmerring’s gazelles (Nanger soemmerringii)

This study focuses on the taxonomic, evolutionary and conservation implications of a striking reduction in body size previously observed in an island population of gazelles by comparing the genetic structure of island and mainland populations. Mitochondrial sequence diversity of the mainland population was found to be comparable to that of other true gazelles of East Africa. We discuss this in the context of the prolonged armed conflict in our study region. In contrast, the gazelles on Dahlak Kebir, one of the over 200 islands and islets of the Dahlak archipelago on the Red Sea, were found to be genetically depauperate. Nucleotide and haplotype diversity estimates were a sixth and a third of that of the mainland population respectively. Using estimates of Tajima’s D statistic, we inferred that the Dahlak population has undergone expansion after a recent bottleneck. A minimum spanning genealogical network of mitochondrial control region sequences produced testable hypotheses on the route and timing of the colonization of Dahlak Kebir by gazelles from the mainland. Our mitochondrial DNA dataset has resolved the taxonomic ambiguity of the island gazelles. Their genetic distinctiveness and, their striking conformity to the Island Rule that was highlighted in a previous study, are discussed from evolutionary and conservation perspectives.