mtDNA Variation in the Altai-Kizhi Population of Southern Siberia: A Synthesis of Genetic Variation

Human Biology, Aug 2006 by Phillips-Krawczak, Christine, Devor, Eric, Zlojutro, Mark, Moffat-Wilson, Kristin, Crawford, Michael H

The network displays proportionately sized circles, which represent observed haplotype frequencies. The reticulation observed within haplogroup C indicates an unresolved evolutionary pathway, with the parallel lines representing the same mutation. The network also displays starlike components within haplogroups C and D, which are features typically associated with an expanding population. Outside haplogroups C and D, a large degree of fragmentation with long internal branches is observed, which may be suggestive of gene flow.

Table 4 contains a comparison of the numbers of shared haplotypes (each haplotype is counted only once) among the three distinct samples from the Altai and various Eurasian populations.

Altai 1 and Altai 3 share the greatest number of common haplotypes (9), whereas Altai 2 shares no haplotypes with Altai 3 and has only one haplotype in common with Altai 1. The Altai 2 sample is based on only 17 individuals, whereas the Altai 1 and Altai 3 samples are based on 61 and 110 individuals, respectively; thus individuals from Altai 1 and 3 are more likely to share common haplotypes. Mongol and Han Chinese sequences reflect their historical connections with the Altai population by sharing 17 and 18 haplotypes with the three combined Altai samples.

Measures of HVS-I sequence diversity are summarized in Table 5 for the three Altai samples, along with the south Siberian, central Asian, Chinese, and Russian populations.

The two θ indexes are derived from different aspects of the mtDNA sequence data, each providing an alternative picture of past evolutionary processes. All the populations in Table 5 display a negative Tajima's D, indicating population expansion. However, two of the three Altai samples fail to exhibit statistically significant deviation from 0 (p

It appears that the Altai 1 sample more closely resembles Tuva and Khakassian populations than the other two Altai samples. Altai 2 and Altai 3 more closely resemble Mongol, Kazakh, Kirghiz, Uighur, and Han Chinese populations.

Mismatch distributions are used to identify characteristics of genetic structure in natural populations that can be attributed to the action of demographic processes (Kingman 1982). Mismatch analyses of the three Altai samples show unimodal peaks, which are predicted for expanding populations (Figure 5).

The distribution of the Altai 1 sample has a mode of 4 and has an additional minor peak at i = 1; this differs from the other two Altai samples, which exhibit modes of 5 and have no secondary minor peaks. Although the Altai 1 distribution appears more ragged than those of the other Altai samples, Harpending's raggedness index (Harpending 1994) is not significant (p > 0.05) for this distribution. When the Altai 1 distribution is compared to the distributions of other Eurasian populations (Figure 6), it appears to be qualitatively more similar to the distributions of the Tuva, which also display a minor peak at i = 1, and the Sojots, with a small peak at i = 0. Similar to Altai 1, neither the Tuva nor the Sojots were significant for the raggedness index.

Coalescent dates in Table 6 were calculated from the τ parameter estimates based on mismatch analyses for the three Altai samples and the other comparative populations.

Overall, the ages range from 67,300 to 95,500 B.P., with the exception of the Russians, which have a later coalescent date (47,300 B.P.), consistent with the findings for other European populations (Richards et al. 2000). Interestingly, the dates for the three Altai samples are remarkably close, ranging from 74,100 to 79,700 B.P., and thus appear to be less affected by sampling than other population genetic statistics.