Studying genetic admixture in South vs. North America

This paper examines whether a subset of AIMs (Ancestry Informative Markers) are useful for looking at admixture among indigenous South American populations, given that these AIMs were developed using North and Central American Native American parental populations. They find little difference between the frequencies of South and North American Native American populations. I wish I had full-text access to this paper to see the results more closely. They looked at 4 tribes in the Amazon. They state in the abstract that those seven AIMs can be used to differentiate between the four tribes. That's surprising to me. Again, I wish I could see the results. Time for inter-library loan, I guess.

Ancestry informative markers in Amerindians from Brazilian Amazon

Marcelo Rizzatti Luizon, Celso Teixeira Mendes-Junior, Silviene Fabiana De Oliveira, Aguinaldo Luiz Simões

American Journal of Human Biology v.19, #6 Nov/Dec 2007

Abstract: Ancestry informative markers (AIMs) are genetic loci with large frequency differences between the major ethnic groups and are very useful in admixture estimation. However, their frequencies are poorly known within South American indigenous populations, making it difficult to use them in admixture studies with Latin American populations, such as the trihybrid Brazilian population. To minimize this problem, the frequencies of the AIMs FY-null, RB2300, LPL, AT3-I/D, Sb19.3, APO, and PV92 were determined via PCR and PCR-RFLP in four tribes from Brazilian Amazon (Tikúna, Kashinawa, Baníwa, and Kanamarí), to evaluate their potential for discriminating indigenous populations from Europeans and Africans, as well as discriminating each tribe from the others. Although capable of differentiating tribes, as evidenced by the exact test of population differentiation, a neighbor-joining tree suggests that the AIMs are useless in obtaining reliable reconstructions of the biological relationships and evolutionary history that characterize the villages and tribes studied. The mean allele frequencies from these AIMs were very similar to those observed for North American natives. They discriminated Amerindians from Africans, but not from Europeans. On the other hand, the neighbor-joining dendrogram separated Africans and Europeans from Amerindians with a high statistical support (bootstrap = 0.989). The relatively low diversity (GST = 0.042) among North American natives and Amerindians from Brazilian Amazon agrees with the lack of intra-ethnic variation previously reported for these markers. Despite genetic drift effects, the mean allelic frequencies herein presented could be used as Amerindian parental frequencies in admixture estimates in urban Brazilian populations.