Ethiopian mitochondrial DNA heritage: tracking gene flow across and around the gate of tears - PubMed (original) (raw)

Comparative Study

doi: 10.1086/425161. Epub 2004 Sep 27.

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Comparative Study

Ethiopian mitochondrial DNA heritage: tracking gene flow across and around the gate of tears

Toomas Kivisild et al. Am J Hum Genet. 2004 Nov.

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Abstract

Approximately 10 miles separate the Horn of Africa from the Arabian Peninsula at Bab-el-Mandeb (the Gate of Tears). Both historic and archaeological evidence indicate tight cultural connections, over millennia, between these two regions. High-resolution phylogenetic analysis of 270 Ethiopian and 115 Yemeni mitochondrial DNAs was performed in a worldwide context, to explore gene flow across the Red and Arabian Seas. Nine distinct subclades, including three newly defined ones, were found to characterize entirely the variation of Ethiopian and Yemeni L3 lineages. Both Ethiopians and Yemenis contain an almost-equal proportion of Eurasian-specific M and N and African-specific lineages and therefore cluster together in a multidimensional scaling plot between Near Eastern and sub-Saharan African populations. Phylogeographic identification of potential founder haplotypes revealed that approximately one-half of haplogroup L0-L5 lineages in Yemenis have close or matching counterparts in southeastern Africans, compared with a minor share in Ethiopians. Newly defined clade L6, the most frequent haplogroup in Yemenis, showed no close matches among 3,000 African samples. These results highlight the complexity of Ethiopian and Yemeni genetic heritage and are consistent with the introduction of maternal lineages into the South Arabian gene pool from different source populations of East Africa. A high proportion of Ethiopian lineages, significantly more abundant in the northeast of that country, trace their western Eurasian origin in haplogroup N through assorted gene flow at different times and involving different source populations.

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Figures

Figure 1

Figure 1

Map of East Africa and Arabia, with locations of samples collected for the present study. The five cities in Ethiopia where DNA samples were collected are indicated. The main spread zones of the five major Ethiopian linguistic groups that are discussed in the study are shown in blue capital letters.

Figure 2

Figure 2

Median joining network of Ethiopian and Yemeni mtDNA haplotypes. Node sizes are proportional to haplotype frequencies, indicated within nodes for

_n_>1

. Haplotypes observed in Ethiopian and Yemeni samples are distinguished by pink and green, respectively. Variable positions (tables A1–A6 [online only]) are indicated along links that connect haplotypes. Nucleotide changes are specified only in the case of transversions. A, Network of haplogroups L0–L6. For haplotypes observed in the Yemeni population, matching HVS-I types in samples from northeastern Africa (Krings et al. ; Stevanovitch et al. 2004) and Mozambique (Pereira et al. ; Salas et al. 2002) are indicated by yellow and blue stars, respectively. B, Network of haplogroups M and N. For haplotypes observed in the Ethiopian population, matching HVS-I types in samples from northeastern Africa (Krings et al. ; Stevanovitch et al. 2004) and in the Arabian Peninsula and Iraq (Richards et al. ; Al-Zahery et al. 2003) are indicated by yellow and blue stars, respectively.

Figure 2

Figure 2

Median joining network of Ethiopian and Yemeni mtDNA haplotypes. Node sizes are proportional to haplotype frequencies, indicated within nodes for

_n_>1

. Haplotypes observed in Ethiopian and Yemeni samples are distinguished by pink and green, respectively. Variable positions (tables A1–A6 [online only]) are indicated along links that connect haplotypes. Nucleotide changes are specified only in the case of transversions. A, Network of haplogroups L0–L6. For haplotypes observed in the Yemeni population, matching HVS-I types in samples from northeastern Africa (Krings et al. ; Stevanovitch et al. 2004) and Mozambique (Pereira et al. ; Salas et al. 2002) are indicated by yellow and blue stars, respectively. B, Network of haplogroups M and N. For haplotypes observed in the Ethiopian population, matching HVS-I types in samples from northeastern Africa (Krings et al. ; Stevanovitch et al. 2004) and in the Arabian Peninsula and Iraq (Richards et al. ; Al-Zahery et al. 2003) are indicated by yellow and blue stars, respectively.

Figure 3

Figure 3

MDS plot of population differences. The plot is based on _F_ST distances (table A7 [online only]) calculated from haplogroup frequencies; its stress value is 0.065.

Figure 4

Figure 4

Phylogeny of mtDNA complete sequences of haplogroup M1. The tree and the character changes are reconstructed by use of maximum-parsimony criteria. Mutations are numbered relative to revised Cambridge Reference Sequence (rCRS) (Andrews 1999). Nucleotide change is specified only for transversions. Sources: MM1 and MM2 = Maca-Meyer et al. (2001); Herrn 287 = Herrnstadt et al. (2002). Haplogroups M1a and M1b are defined as in figure 2_B_ and tables A1–A6 (online only), by polymorphisms identified by Quintana-Murci (1999). Character-state changes at nps 16129 and 16359, shown in parentheses on the external branch of the Herrnstadt et al. (2002) coding-region sequence, are inferred from the complete linkage of the 12346 polymorphism with the derived status at these positions in the present study.

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References

Electronic-Database Information

    1. ADMIX 2.0, http://web.unife.it/progetti/genetica/Isabelle/admix2_0.html
    1. ARLEQUIN package, http://lgb.unige.ch/arlequin/
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