Rodrigo Flores-Espinoza1,2, Elius Paz-Cruz3, Viviana A Ruiz-Pozo3, Marcelo Lopez-Carrera3, Alejandro Cabrera-Andrade4,5, Leonor Gusmão1, German Burgos6,7. 1. Laboratório de Diagnóstico por DNA (LDD), Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil. 2. Laboratorios de Investigación, Universidad de Las Américas (UDLA), Quito, Ecuador. 3. Laboratorio de ADN, Fiscalía General del Estado, Quito, Ecuador. 4. Grupo de Bio-Quimioinformática, Universidad de Las Américas (UDLA), Quito, Ecuador. 5. Carrera de Enfermería, Facultad de Ciencias de la Salud, Universidad de Las Américas (UDLA), Quito, Ecuador. 6. Escuela de Medicina, Facultad de Ciencias de la Salud, Universidad de Las Américas (UDLA), Quito, Ecuador. 7. Grupo de Medicina Xenómica, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Abstract
OBJECTIVES: According to demographic history, Ecuador has experienced shifts in its Native American populations caused by European colonization and the African slave trade. The continuous admixture events among Europeans, Native Americans, and Africans occurred differently in each region of the country, producing a stratified population. Thus, the aim of this study was to investigate the level of genetic substructure in the Ecuadorian Mestizo population. MATERIALS AND METHODS: A total of 377 male and 209 female samples were genotyped for two sets of X-chromosomal markers (32 X-Indels and 12 X-STRs). Population analyses performed included Hardy-Weinberg equilibrium tests, LD analysis, PCA, pairwise FST s, and AMOVA. RESULTS: Significant levels of LD were observed between markers separated by distances of less than 1 cM, as well as between markers separated by distances varying from 10.891 to 163.53 cM. Among Ecuadorian regions, Amazonia showed the highest average R2 value. DISCUSSION: When X-chromosomal and autosomal differentiation values were compared, a sex-biased admixture between European men and Native American and African women was revealed, as well as between African men and Native American women. Moreover, a distinct Native American ancestry was discernible in the Amazonian population, in addition to sex-biased gene flow between Amazonia and the Andes and Pacific coast regions. Overall, these results underline the importance of integrating X chromosome information to achieve a more comprehensive view of the genetic and demographic histories of South American admixed populations.
OBJECTIVES: According to demographic history, Ecuador has experienced shifts in its Native American populations caused by European colonization and the African slave trade. The continuous admixture events among Europeans, Native Americans, and Africans occurred differently in each region of the country, producing a stratified population. Thus, the aim of this study was to investigate the level of genetic substructure in the Ecuadorian Mestizo population. MATERIALS AND METHODS: A total of 377 male and 209 female samples were genotyped for two sets of X-chromosomal markers (32 X-Indels and 12 X-STRs). Population analyses performed included Hardy-Weinberg equilibrium tests, LD analysis, PCA, pairwise FST s, and AMOVA. RESULTS: Significant levels of LD were observed between markers separated by distances of less than 1 cM, as well as between markers separated by distances varying from 10.891 to 163.53 cM. Among Ecuadorian regions, Amazonia showed the highest average R2 value. DISCUSSION: When X-chromosomal and autosomal differentiation values were compared, a sex-biased admixture between European men and Native American and African women was revealed, as well as between African men and Native American women. Moreover, a distinct Native American ancestry was discernible in the Amazonian population, in addition to sex-biased gene flow between Amazonia and the Andes and Pacific coast regions. Overall, these results underline the importance of integrating X chromosome information to achieve a more comprehensive view of the genetic and demographic histories of South American admixed populations.