EVIDENCE OF LIMITED GENE FLOW IN 3 SPECIES OF CORAL-REEF FISHES IN THE LAGOON OF NEW-CALEDONIA

Allozyme variation was used to investigate the genetic structure of th e coral reef fishes Stegastes nigricans, Epinephelus merra and Acanthu rus triostegus around New Caledonia. Each species was sampled from eac h of three sites in the similar or equal to 1000 km circumference of t he lagoon of New Caledonia. Allelic variation was recorded for each sp ecies at 14, 13 and 17 loci, respectively, and heterozygosity diversit y (H-S) was 0.082, 0.065 and 0.116, respectively. Analysis of genetic differentiation between sites produced inconsistent results between sp ecies, with spatial heterogeneity in two species (S. nigricans, F-ST = 0.038; A. triostegus, F-ST = 0.049) and homogeneity in one species (E . merra, F-ST = 0.000). Hydrological and climatic data from the lagoon suggest that the eastern and western sides of the lagoon are isolated , since they lie in water masses of different origin. This may explain the genetic differentiation and restricted gene flow found at a local scale for S. nigricans and A. triostegus. Homogeneity in populations of E. merra is discussed in relation to its low genetic diversity and its reproductive behaviour.