DISPERSAL AND EVOLUTION OF THE PACIFIC BASIN GEKKONID-LIZARDS GEHYRA-OCEANICA AND GEHYRA-MUTILATA

The Pacific island geckos Gehyrn mutilata and Gehyra oceanica were stu died on several Pacific Basin archipelagos to determine the degree tha t their distributions have been modified by humans (as commensals), th rough the analysis of protein variation using starch gel electrophores is. Gehyra mutilata is an anthropophilic species that is widespread in the Pacific Basin and Southeast Asia. No protein variation was found in the Pacific Basin and southern Asia, although there were fixed alle lic differences between populations of southern Asia and those further north. These results suggest possible recent human-aided transport ac ross the Pacific from a population that experienced a genetic bottlene ck in southern Asia. Gehyra oceanica, based on protein variation, cons ists of two natural groups in the Pacific, a northern (Micronesian) fo rm and a southern (Melanesian and Polynesian) form. The northern form has very similar gene frequencies across its range in Micronesia. The southern form has its greatest allelic diversity in the southcentral P acific. F-statistics for G. oceanica in the south fall within the rang e of values in the literature for mainland Australian species of Gehyr a that are not human commensals and for other island lizards that have been considered as natural dispersers. These values are consistent wi th the hypothesis that G. oceanica was naturally dispersed across the Pacific, prior to the arrival of humans and that the equatorial curren ts are a barrier to natural, north-south gene flow/dispersal in Pacifi c Basin lizards. However human-aided dispersal within the northern and southern regions cannot be ruled out. By comparing the ecology of the se two species, G. oceanica has the adaptations necessary for natural oversea dispersal, whereas G. mutilata has an ecology consistent with human-mediated dispersal, in support of the conclusions from the genet ic data.