Phylogeny and genetic structure of Tunisians and their position within Mediterranean populations

Abstract

Tunisia is located at the crossroads of Europe, the Middle East and Sub-Saharan Africa. This position might lead to numerous waves of migrations, contributing to the current genetic landscape of Tunisians. In this study, we analyzed 815 mitochondrial DNA (mtDNA) sequences from Tunisia in order to characterize the mitochondrial DNA genetic structure of this region, to construct the processes for its composition and to compare it to other Mediterranean populations. To that end, additional 4206 mtDNA sequences were compiled from previous studies performed in African (1237), Near Eastern (231) and European (2738) populations. Both phylogenetic and statistical analyses were performed. This study confirmed the mosaic genetic structure of the Tunisian population with the predominance of the Eurasian lineages, followed by the Sub-Saharan and North African lineages. Among Tunisians, the highest haplogroup and haplotype diversity were observed in particular in the Capital Tunis. No significant differentiation was observed between both geographical (Northern versus Southern Tunisia) and different ethnic groups in Tunisia. Our results highlight the presence of outliers and most frequent unique sequences in Tunisia (10.2%) compared to 45 Mediterranean populations. Phylogenetic analysis showed that the majority of Tunisian localities were closer to North Africans and Near Eastern populations than to Europeans. The exception was found for Berbers from Jerba which are clustered with Sardinians and Valencians.

Lactase persistence in Tunisia as a result of admixture with other Mediterranean populations

“…2 ). This is in agreement with previous studies that examined uniparental and autosomal markers and showed a multi-ethnic origin of North Africans [ 27 , 37 , 46 ].…”

“…The obtained results were discussed in the light of the relatively recent historical relationships between Tunisian and the abovementioned populations [ 27 , 53 , 54 ], in the attempt to clarify the routes followed by LP diffusion and to explore the potential processes of convergent evolution of LP in European and in some non-European populations, such as the Tunisian one.…”

“…Indeed, the age estimate for the − 13,910 T variant ranges from 12,300 to 5000 years ago [ 4 , 20 , 21 , 24 , 25 ], which broadly coincides with the origins of cattle domestication in North Africa and Levant around 10,000 years ago [ 26 ]. Indeed, the origin of the pastoral movement from the East and West of Africa to Tunisia was dated to the trading of gold, salt, and slaves across the Sahara [ 27 ]. Genetic studies conducted on populations from this area and performed using mitochondrial DNA (mtDNA) and nuclear markers confirmed also a correlation between genetic and geographic structure and/or distances [ 28 ] and a predominantly east-west structure [ 29 ].…”

“…Tunisia has a geostrategic location since it represents a crossroad between Europe, the Middle East and Sub-Saharan Africa and a stepping-stone for recent human migrations. Therefore, the genetic background of the present Tunisian population may have been influenced by these migrations and the successive invasions of the country [ 27 , 37 ]. The main focus of this study is thus to explore variation patterns of a large number of single nucleotide polymorphisms (SNPs) located in the LCT/MCM6 region, potentially related to the LP phenotype.…”

Ancient and recent Middle Eastern maternal genetic contribution to North Africa as viewed by mtDNA diversity in Tunisian Arab populations

“…This was marked by the invasion of Bedouin tribes (Banu Hilal), followed by the Arabization and Islamization of many Berber populations. Even so, previous studies on Tunisian populations displayed the mosaic structure of the mitochondrial gene pool, which is characterized by an overall high frequency of Eurasian haplogroups (∼70%), followed by Sub‐Saharan L lineages (∼ 25%), and lesser frequencies of North African haplogroups U6 and M1 (5%) (Fadhlaoui‐Zid et al, ; Frigi et al, ; Kefi et al, ). However, of these mtDNA, only Fernandes et al () estimated the recent contribution of Near Eastern sublineages, i.e., K1a1, N1, T, J, R0a, U, and X, suggesting that they arrived around 2000 years ago, probably associated with Phoenician occupation.…”