The ancestry of Y-chromosomes in Puerto Rico. K. Ocasio-González, A. Díaz-Lameiro, K. Martínez-Vargas, M. López-Muñoz, J.C. Nazario-Borges, J.C. Martínez-Cruzado Department of Biology, University of Puerto Rico at Mayagüez, Mayagüez, PR.

   Most Latin American populations show asymmetric ancestry, with European ancestry predominating in the paternal lineages and Amerindian or African ancestry in the maternal lineages. In consistency with this pattern, the female ancestry of Puerto Ricans has recently been shown to be predominantly Amerindian, followed by African and West Eurasian ancestries in that order. In a progressing program of research, we have identified the haplogroup of 202 Puerto Rican Y-chromosomes through biallelic marker typing and estimated that 151 (74.8%) are of West Eurasian origin, 48 (23.8%) Sub-Saharan African, and 3 (1.5%) Amerindian. In addition, 17 Y-STR loci of 35 samples have been typed, producing 32 haplotypes, the haplogroup of 18 of which have been identified through biallelic markers. The Y-STR data was used to construct a median-joining network that produced five clusters of 18, 4, 3, 3, and 3 haplotypes each. One haplotype of haplogroup still unknown remained separated from all five clusters. Y-STR-haplogroup matching analysis strongly suggested that all Y-chromosomes belonging to each Y-STR cluster shared the same continental origin. For example, all 11 haplotypes for which the haplogroup was known in the 18-haplotype cluster belonged to West Eurasian haplogroup R1b. In that way, two clusters totaling 21 haplotypes, were identified as West Eurasian in origin, and two clusters totaling 7 haplotypes as Sub-Saharan African. The haplogroups of none of the three haplotypes of the remaining cluster have yet been identified. A search in the Y-chromosome haplotype reference database produced results consistent with the deduced origin of the clusters, and suggested that the origin of the remaining cluster is Asian or Native American. It did not suggest an origin for the isolated haplotype. We conclude that, as in other Latin American populations, the continental origin frequency of Y-chromosomes in Puerto Rico is inverted relative to that of mtDNA. We further conclude that Y-STR haplotypes are excellent predictors of haplogroup identity.