Ancestral reconstruction and correlation of the frequencies of the hemoglobin S allele and the Duffy blood group alleles in human populations.

Abstract

Malaria is an important selective force for human genetic adaptation due to the sustained, lethal impact it has had on populations worldwide. High frequencies of both hemoglobin S and the null allele FYBES of the Duffy blood group have been found in areas where this disease is endemic, attributed to the protective action of the carriers of these variants against malaria infection. The objective of this work was to perform ancestral reconstruction and analyze the correlation of the frequencies of these alleles throughout the phylogeny of 24 human populations. A tree topology and the allelic frequencies reported in the literature for the 24 populations were used. The ancestral frequencies for the two alleles were reconstructed using the maximum likelihood method and the Brownian model of evolution (CI=95%), and the correlation analysis was performed using phylogenetically independent contrasts (PICs). Statistical analyses were performed with the statistical software R version 3.4.1. For both alleles, a correspondence was found in the reconstruction of the ancestral frequencies, and a significant statistical correlation (p=.001) was observed between the S and FYBES alleles. These results provide evidence of an epistatic relationship between the two alleles, which may influence the fitness of the individuals who present with them when they are subjected to a selective force such as malaria.