Global Patterns in Human Mitochondrial DNA and Y-Chromosome Variation Caused by Spatial Instability of the Local Cultural Processes

Abstract

Because of the widespread phenomenon of patrilocality, it is hypothesized that Y-chromosome variants tend to be more localized geographically than those of mitochondrial DNA (mtDNA). Empirical evidence confirmatory to this hypothesis was subsequently provided among certain patrilocal and matrilocal groups of Thailand, which conforms to the isolation by distance mode of gene diffusion. However, we expect intuitively that the patterns of genetic variability may not be consistent with the above hypothesis among populations with different social norms governing the institution of marriage, particularly among those that adhere to strict endogamy rules. We test the universality of this hypothesis by analyzing Y-chromosome and mtDNA data in three different sets of Indian populations that follow endogamy rules to varying degrees. Our analysis of the Indian patrilocal and the matrilocal groups is not confirmatory to the sex-specific variation observed among the tribes of Thailand. Our results indicate spatial instability of the impact of different cultural processes on the genetic variability, resulting in the lack of universality of the hypothesized pattern of greater Y-chromosome variation when compared to that of mtDNA among the patrilocal populations.

Larger mitochondrial DNA than Y-chromosome differences between matrilocal and patrilocal groups from Sumatra

“…Unexpectedly, and in contrast to virtually every other study of human mtDNA versus NRY diversity on the local scale, there are no significant differences between these two groups for the NRY. Moreover, our results highlight the importance of obtaining complete mtDNA genome sequences, as there are no significant differences in HD between the Besemah and Semende when only partial sequences are analysed, as was done in previous studies 7,8 . Results mtDNA sequences.…”

“…In particular, perhaps the failure of identifing such differences in previous studies is due to the lack of power using only the HV1 (ref. 7) or only a single gene such as…”

“…Indeed, this prediction was fulfilled in the first comparison of patterns of mtDNA and NRY variation in matrilocal and patrilocal groups, among the hill tribes of Thailand 4,6 . However, a subsequent study of matrilocal and patrilocal groups in India failed to find the predicted patterns of mtDNA versus NRY diversity 7 , whereas another study has called into question the original observation of larger differences among human groups in general for the NRY versus mtDNA 8 . Clearly, studies of additional matrilocal groups are needed to ascertain if there is a general effect of residence pattern on human mtDNA and NRY diversity.…”

“…Furthermore, the F ST value for the mtDNA is 0.076 and is significantly different from 0 (P = 0). As a previous study that failed to find a difference in patterns of mtDNA diversity between matrilocal and patrilocal groups in India only sequenced the HV1 region 7 , we also analysed only the HV1 sequences from the Semende and Besemah. In contrast to the results based on complete mtDNA genome sequences, the difference in mtDNA HD is not significant between the Semende and Besemah ( Supplementary Fig.…”

The role of matrilineality in shaping patterns of Y chromosome and mtDNA sequence variation in southwestern Angola

“…In the last few years, various studies took advantage of the increasing availability of next generation sequencing (NGS) platforms to compare unbiased NRY and mtDNA sequence data on a global scale [4][5][6][7] . Nevertheless, the sex-specific patterns disclosed by worldwide studies reflect average trends exhibited by different macro-regions, and do not explore the rich diversity of interactions between genetic variation and cultural practices that shape NRY and mtDNA variation at the local level 8 .…”