Admixture and sexual bias in the population settlement of La Réunion Island (Indian Ocean)

Abstract

La Réunion, one of the three Mascarene islands located in the Indian Ocean, remained devoid of inhabitants until it was first colonized by the French in the middle of the 17th century. The continuous flow of foreign-born slaves and immigrant workers from Africa, India, Southeast Asia, and China to work on coffee and sugar cane plantations led to the island becoming a melting pot of people of multiple ethnic origins. To establish the impact of the different incoming ethnic groups on the present Reunionese gene pool, we have sequenced both hypervariable regions I and II of the mitochondrial DNA molecule, the 9 bp COII/tRNA(Lys) deletion, and four SNPs located in the coding region in a total of 41 samples of the general population, and a further 18 STRs and 35 SNPs on the Y chromosome in 26 of these samples. Our results show that there was a strong sexual bias (asymmetrical gene flow) in the peopling of La Réunion, where admixture events were mainly between male settlers and females from the incoming slave groups. Most of the Y-chromosome gene pool is of European/Middle Eastern ancestry (85%), whereas the mtDNA gene pool is mainly of Indian and East Asian ancestry (70%). The absence of genetic diversity within these two major components of the mtDNA gene pool suggests these populations may have witnessed strong founder effects during the colonization process.

Multiple Ethnic Origins of Mitochondrial DNA Lineages for the Population of Mauritius

“…A similar result was obtained for the Comoro Archipelago [8], [9]. In relation to Réunion Island, phylogeographic analysis not only detected strong founder effects and gender asymmetrical gene flow [10] but also tracked the most probable origins of the Malbar and Zarab ethnic groups [11].…”

“…The Reunionese sample from Berniell-Lee et al (2008) [10] was used only for match analysis as it is not comparable with our miscellaneous sample from Mauritius due to founding events affecting its mtDNA diversity and its low representativeness of the whole population of Réunion [11]. The sample from the Dubut et al (2009) study [11] could only be used for determining differences between Indian influences as it is based on the characterization of two concrete ethnic groups of Indian origin, the Malbar and the Zarab .…”

Genetic origin, admixture, and asymmetry in maternal and paternal human lineages in Cuba

“…See for instance, figures 9.16 and 9.18 in Jobling et al [13]. In admixed populations, mtDNA sequences and Y-chromosome haplotypes can be assigned to a continent of origin [14]. In this study we analyzed the complementary information provided by both markers with the aim of surveying (i) the geographic origin of current Cuban ancestors, (ii) the extent of the admixture present among these, and (iii) their differential sexual contribution to the present-day Cuban gene pool.…”

Autosomal Admixture Levels Are Informative About Sex Bias in Admixed Populations

“…In the Americas, these include African American, Latino, and Native American populations (Bolnick et al 2006; Wang et al 2008; Stefflova et al 2009; Tishkoff et al 2009; Bryc et al 2010a,b; Moreno-Estrada et al 2013; Verdu et al 2014). Sex-biased admixture and migration have also been examined in populations throughout Asia (Oota et al 2001; Wen et al 2004; Chaix et al 2007; Ségurel et al 2008; Chaubey et al 2011; Pemberton et al 2012; Pijpe et al 2013), Austronesia (Kayser et al 2003, 2006, 2008; Cox et al 2010; Lansing et al 2011), and Africa (Wood et al 2005; Tishkoff et al 2007; Berniell-Lee et al 2008; Beleza et al 2013; Petersen et al 2013; Verdu et al 2013). …”