mtDNA of Fulani Nomads and Their Genetic Relationships to Neighboring Sedentary Populations

Human Biology, Feb 2006 by Cerný, V, Hájek, M, Bromová, M, Cmejla, R, Et al

Results

mtDNA Haplogroups. The total sample from the four geographically distinct Fulani populations (n = 186) yielded 58 haplotypes, which were classified into 14 haplogroups (see Appendix 1); as expected, a significant majority belonged to sub-Saharan type L. The most numerous haplogroups are L3b (determined by the motif 16124, 16223, 16278, and 16362) and L3d (determined by the motif 16124 and 16223); these two haplogroups could not be distinguished from each other when only the HVS-I sequence was available. However, because both share the same geographic origin in West Africa, the HVS-II motif and RFLP polymorphisms were not further studied for a more specific molecular determination. Together, the L3b and L3d haplogroups contain 62 sequences with 12 haplotypes.

The second well-diversified haplogroup found in the Fulani nomads sample is L1b (50 sequences, 10 haplotypes), with the determining HVS-I motif 16126, 16187, 16189, 16223, 16264, 16270, 16278, and 16311, the origin of which also lies in West Africa (Salas et al. 2002, 2004).

All the other haplogroups identified are represented by conspicuously lower numbers; the most numerous among them, comparatively speaking, are L2b and L2c, which are also of West African origin. It is interesting that the otherwise common L2a haplogroup (determined by mutation at np 16294) is not present to any great degree in the overall sample. The distribution of the haplotypes in each of the sampled Fulani populations is quite even-all the aforementioned (more numerous) haplogroups were present in each population sample at comparable frequencies. In addition, it is worth noting that 15 sequences (8.1%) of North African/Eurasian origin (U5, V, J1b, and one sequence corresponding to the Cambridge Reference Sequence) occurred.

We have detected new mutations in the L1b haplogroup, which is otherwise well classified by HVS-I mutations at np 16126, 16187, 16189, 16223, 16264, 16270, 16278, and 16311 (Salas et al. 2002). The L1b network (Figure 2) shows that most of the Fulani mtDNA sequences fall within clade L1b1, which is determined by the presence of a mutation at np 16293 plus the aforementioned L1b motif. One haplotype with a mutation at np 16170, not yet reported elsewhere, was observed for one individual from Banfora (Burkina Faso), and two new haplotypes-one presenting a mutation at np 16093 (one Fulani from Bongor, Chad) and the other a mutation at np 16255 (one Fulani from Tindangou)-were also observed. Also, in the L1b* haplogroup there is a new haplotype with a mutation at np 16368.

Molecular Diversity. The indexes of genetic diversity for all four Fulani samples are given in Table 2. The gene diversities reach values between 0.893 and 0.953 (for the merged population, 0.936). This measure, considered equivalent to heterozygozity in haplotype studies (Schneider et al. 2000), together with the nucleotide diversity and the average number of pairwise differences attains values similar to those known from other sub-Saharan populations (Cerný et al. 2004). On the other hand, the relatively low levels of the raggedness index are interesting; in one sample from Burkina Faso (Tindangou) this index even attains statistical significance. Tajima's D test of selective neutrality, based on the infinite-site model of the studied groups, was not significant in any of the samples. Fu's F^sub S^-which is much more sensitive to population demographic expansions and is highly significant (p ≤ 0.001) in all agricultural populations [see Pereira et al. (2001, Table 3)]-is significant only for the Fulani sample from Bongor. Significant levels were obtained from merged Fulani groups in the Chad basin or when all four Fulani samples were merged (n = 97). However, the Fulani from Burkina Faso, when taken together, did not attain a statistically significant value. Neglecting the hypothesis of selection, the nonsignificant values of the D and F^sub S^ statistics provide an indication of reduced demographic expansion hitherto observed mainly in hunter-gather populations such as the Pygmies or Khoisan (Excoffier and Schneider 1999).