Diversity and Divergence Among the Tribal Populations of India

Abstract

SummaryTribal populations of the Indian subcontinent have been of longstanding interest to anthropologists and human geneticists. To investigate the relationship of Indian tribes to Indian castes and continental populations, we analyzed 45 unlinked autosomal STR loci in 9 tribal groups, 8 castes, and 18 populations from Africa, Europe and East Asia. South Indian tribal populations demonstrate low within-population heterozygosity (range: 0.54 -0.69), while tribal populations sampled further north and east have higher heterozygosity (range: 0.69 -0.74). Genetic distance estimates show that tribal Indians are more closely related to caste Indians than to other major groups. Between-tribe differentiation is high and exceeds that for eight sub-Saharan African populations (4.8% vs. 3.7%). Telugu-speaking populations are less differentiated than non-Telugu speakers (F ST : 0.029 vs. 0.079), but geographic distance was not predictive of genetic affinity between tribes. South Indian tribes show significant population structure, and individuals can be clustered statistically into groups that correspond with their tribal affiliation. These results are consistent with high levels of genetic drift and isolation in Indian tribal populations, particularly those of South India, and they imply that these populations may be potential candidates for linkage disequilibrium and association mapping.

Fine-scaled human genetic structure revealed by SNP microarrays

“…The tribal Irula population also exhibits more interindividual variation but lower overall heterozygosity than do the caste populations. This difference is likely to reflect the greater degree of genetic drift in small isolated groups within the Irula population (Watkins et al 2005). Since the Irula individuals in this study were sampled from two locations in southern Andhra Pradesh, it is possible that the genetic structure observed within this population may reflect differences in sampling locality.…”

“…Our analyses also shed additional light on the genetic structure of Indian populations, which has been the subject of much research and debate (Bamshad et al 1998(Bamshad et al , 2001Basu et al 2003;Vishwanathan et al 2004;Watkins et al 2005Watkins et al , 2008Rosenberg et al 2006;Chaubey et al 2007). Our results show relatively larger genetic distances between the caste and tribal populations than among caste populations (Fig.…”

“…Next, we calculated pairwise F ST between populations (Supplemental Table 1 A large proportion of individuals included in this study have been genotyped previously for other types of polymorphisms (Jorde et al 1997;Watkins et al 2003Watkins et al , 2005Wooding et al 2004). For these individuals, we examined the concordance of between-population genetic distances based on the high-density SNP data and other types of autosomal polymorphisms.…”

“…The origins of and relationships among Indian populations are the subjects of continuing debate (Bamshad et al 1998(Bamshad et al , 2001Basu et al 2003;Vishwanathan et al 2004;Watkins et al 2005;Rosenberg et al 2006;Chaubey et al 2007), but most previous genetic studies of these populations have been based on modest data sets. Indian populations are also used increasingly in linkage and case-control studies of genetic disease (Alcais et al 2007;Chambers et al 2008;Holliday et al 2008).…”

Genetic Similarities Within and Between Human Populations

“…The first data set (''insertions'') consists of 175 polymorphic transposable element insertion loci (100 Alu and 75 L1) previously genotyped in 259 individuals. The population sample consists of 104 individuals from sub-Saharan Africa, 54 East Asians, 61 individuals of northern European ancestry, and 40 individuals from Andhra Pradesh, India (Watkins et al 2005;Witherspoon et al 2006). The second data set (''microarray'') consists of 9922 biallelic single-nucleotide polymorphism (SNP) loci genotyped in 278 individuals (55 Africans, 42 African Americans, 40 Native Americans, 22 Indians, 20 East Asians, 62 Europeans, 18 Hispano-Latinos from Puerto Rico, and 19 individuals from New Guinea).…”