Migration and isolation effects on the Rapanui population (Easter island) through the analysis of STRs on the Y chromosome

Cultural and biological data suggests the Polynesian origin of the Rapanui population, although the presence of foreign genes in the native population, as a result of admixture with Europeans in the last two centuries has also to be considered. In order to estimate the genetic affinities of the present-day inhabitants of Easter Island and the nearby populations, we used seven polymorphisms of the Y chromosome. However we want to estimate the grade of admixture on the genetic structure that was brought from foreigners within the last two centuries upon the more geographically isolated populations in the world. The preliminary results showed the presence of 18 haplotypes analyzed on 30 male samples. The analysis of the allelic frequency showed a distribution typical of the Polynesian populations. Available data in literature, even with some differences probably due to either the founder effect or historical and ecological events that created sudden demographic variations on the island population. The phylogentic analysis of the haplotypes obtained through Network Median Joining showed two different cluster of haplotypes, of which one represents about 64% of the present haplotypes on Easter Island, which are characterized from the presence of the allele DYS19^*16, very frequent in the Pacific populations. The other cluster is characterized from the presence of the allele DYS19^*14, absent within the populations in the Pacific and with reasonable high frequency within the European populations and South American. Most probably the two clusters are the product of several colonizations that Easter Island had endured from the time of the Chilian and European Colonies. It was demonstrated in fact, that the arrival in 1914 of 50 German and English prisoners would have left a considerable genetic impact on the population of Rapanui, which during this period was of small size.