Mitochondrial and nuclear genetic relationships among Pacific Island and Asian populations

Mitochondrial and autosomal short tandem-repeat (STR) genetic distances among 28 Pacific Island and Asian populations are significantly correlated (r = .25, P < .01) but describe distinct patterns of relationships. Maternally inherited-mtDNA data suggest that Remote Oceanic Islanders originated in island Southeast Asia. In contrast, biparental STR data reveal substantial genetic affinities between Remote Oceanic Islanders and Near Oceanic populations from highland Papua New Guinea and Australia. The low correlation between maternal and biparental genetic markers from the same individuals may reflect differences in genome-effective population sizes or in sex-biased gene flow. To explore these possibilities, we have examined genetic diversity, gene flow, and correlations among genetic, linguistic, and geographic distances within four sets of populations representing potential geographic and cultural spheres of interaction. G(ST) estimates (a measure of genetic differentiation inversely proportional to gene flow) from mtDNA sequences vary between 0.13 and 0.39 and are typically five times greater than G(ST) estimates from STR loci (0.05-0.08), Significant correlations (r > .5, P < .05) between maternal genetic and linguistic distances are coincident with high mtDNA G(ST) estimates (>0.38). Thus, genetic and linguistic distances may coevolve, and their correspondence may be preserved under conditions of genetic isolation. A significant correlation (r = .65, P < .01) between biparental genetic and geographic distances is coincident with a low STR G(ST) estimate (0.05), indicating that isolation by distance is observed under conditions of high nuclear-gene flow. These results are consistent with an initial settlement of Remote Oceania from island Southeast Asia and with extensive postcolonization male-biased gene flow with Near Oceania.