Deep genetic divergence underlies within-island eco-morphological variation in the endangered day gecko Phelsuma borbonica: implications for conservation

The day gecko Phelsuma borbonica displays marked differences in coloration and occupies a variety of habitats across its very small range on the volcanic oceanic island of Reunion in the southwestern Indian Ocean. Such differences might reflect geographic and ecological divergence and thus be associated with an underlying genetic differentiation. We examined the partitioning of genetic diversity in Phelsuma borbonica across Reunion at a very small spatial scale (< 10 km) using mtDNA and nuDNA sequences, along with microsatellite genotype data. This study provides an account of the evolutionary history of Phelsuma borbonica, along with a quantification of effective population sizes, which constitute important information for the conservation of this endangered species, which may represent a previously unrecognized case of incipient speciation. We found that populations of Phelsuma borbonica are genetically strongly differentiated, highlighting historically low levels of gene flow. Phylogenetic analyses suggest that Phelsuma borbonica reached its present range through two parallel southward expansions from an ancestral population located in the northern part of the island.