Inter‐ and Extra‐Indian Admixture and Genetic Diversity in Reunion Island Revealed by Analysis of Mitochondrial DNA

Abstract

SummaryReunion Island is a French territory located in the western Indian Ocean. The genetic pattern of the Reunionese population has been shaped by contributions from highly contrasting regions of the world. Over the last 350 years, several migration waves and cultural and socio-economic factors have led to the emergence of six main ethnic groups in Reunion. India is one of the principal regions that contributed to the setting up of the Reunionese population. Diversity, demographic and admixture analyses were performed on mtDNA variation of the Reunionese of Indian ancestry, including the Malbar and Zarab ethnic groups, in order to question their history. Using a phylogeographical approach, we generated and analysed quantitative data on the contribution of the Indian parental populations. Furthermore, we showed that the settlement of Reunion Island by Indians did not involve a founder effect, except in the very beginning of the Reunionese settlement (at the end of the 17 th century). The accuracy of our results was optimised by a re-evaluation of the classification of the Southern Asian mtDNA haplogroups. Finally, by comparing our results to a previous study dealing with the Reunionese population, we highlighted how ethno-historical data are critical for reconstructing the complex history of multiethnic populations.

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 .…”

Origins, admixture and founder lineages in European Roma

“…We used a database with a total of 641 Indian Y-chromosomes from five regions, 44 excluding the Northeastern populations, of Tibeto-Burman origin, and searched for identical matches of H-M52 Roma haplotypes. Identical matches for the mtDNA M lineages were assessed by comparison with the Indian database 45 as in Medizabal et al 46 The weighted proportion of Roma lineages was used to infer the probabilities of origin. Table S1).…”

Indian Signatures in the Westernmost Edge of the European Romani Diaspora: New Insight from Mitogenomes

“…M18 is completely absent in Central and Eastern European Romani. The great majority of M18 haplotypes are found in Southwest India (where M18 constitutes ∼2% of the lineages; [31]); and few appear also in the Malbars from the Reunion Island, which are known to be mainly of Indian ancestry [31].…”

“…Admixture estimates were previously obtained on mtDNA data based on an algorithm that weighs matched haplotypes existing between the source population (India) and the Romani [22]; however, it is important to note that many South Asian haplotypes existing in the Romani are not present in the source Asian population (although their phylogeographic characteristics point to their undoubtedly Asian origin). For instance, the most characteristic Romani M5a1b1a1 haplotype (the one that matches the motif of M5a1b1a1 and that constitutes 15% of the total mtDNA Romani pool; Table S2 ) of Indian origin is very rare in India (0.001%; [31]). Therefore, as per the algorithm mentioned above, this Indian haplotype would not contribute to the Indian ancestry proportion of the Romani (e.g.…”