GEOGRAPHIC STRUCTURE OF MITOCHONDRIAL AND NUCLEAR GENE POLYMORPHISMS IN AUSTRALIAN GREEN TURTLE POPULATIONS AND MALE-BIASED GENE FLOW

The genetic structure of green turtle (Chelonia mydas) rookeries locat ed around the Australian coast was assessed by (1) comparing the struc ture found within and among geographic regions, (2) comparing microsat ellite loci vs. restriction fragment length polymorphism analyses of a nonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic s tructure was observed over all regions at both sets of nuclear markers , though the microsatellite data provided greater resolution in identi fying significant genetic differences in pairwise tests between region s. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter bei ng more congruent with geography. Estimated rates of gene flow were ge nerally higher than expected for nuclear DNA (nDNA) in comparison to m tDNA, and this difference was most pronounced in comparisons between t he northern and southern Great Barrier Reef (GBR). The genetic data co mbined with results from physical tagging studies indicate that the la ck of nuclear gene divergence through the GBR is likely due to the mig ration of sGBR turtles through the courtship area of the nGBR populati on, rather than male-biased dispersal. This example highlights the val ue of combining comparative studies of molecular variation with ecolog ical data to infer population processes.