Population structure in two species of the reef goby Gnatholepis (Teleostei: Perciformes) among four South Pacific island groups

Abstract

Individuals of two species in the reef goby genus Gnatholepis ( G. anjerensis and G. scapulostigma) were sampled from across the South Pacific, including the Society Islands, the Tuamotu Archipelago, the Cook Islands, and Fiji. The two species examined differ in habitat preference, with one (G. anjerensis) preferring shallow, lagoon habitats, and the other (G. scapulostigma) usually occupying habitats outside the lagoons. Partial sequence of the mitochondrial ND2 gene (451–483 base pairs) was determined for 267 individuals and analyzed for demographic structure, population structuring, and correlation of population structure with geographic distance between populations. Both species exhibit demography characteristic of population expansion in the Pleistocene, approximately 88,000 years ago for G. anjerensis and 237,000 years ago for G. scapulostigma. Comparisons of Φ st indicate more structuring among populations of G. anjerensis than G. scapulostigma, although only G. scapulostigma shows a significant correlation between geographic distance and population divergence. It is postulated that the population expansions in Gnatholepis species are related to Pleistocene fluctuations in sea level, and that the ecology of G. anjerensis populations may contribute to their greater population structuring.