Analysis of the human Y-chromosome haplogroup Q characterizes ancient population movements in Eurasia and the Americas

Background: Recent genome studies of modern and ancient samples have proposed that Native Americans derive from a subset of the Eurasian gene pool carried to America by an ancestral Beringian population, from which two well-differentiated components originated and subsequently mixed in different proportion during their spread in the Americas. To assess the timing, places of origin and extent of admixture between these components, we performed an analysis of the Y-chromosome haplogroup Q, which is the only Pan-American haplogroup and accounts for virtually all Native American Y chromosomes in Mesoamerica and South America. Results: Our analyses of 1.5 Mb of 152 Y chromosomes, 34 re-sequenced in this work, support a "coastal and inland routes scenario" for the first entrance of modern humans in North America. We show a major phase of male population growth in the Americas after 15 thousand years ago (kya), followed by a period of constant population size from 8 to 3 kya, after which a secondary sign of growth was registered. The estimated dates of the first expansion in Mesoamerica and the Isthmo-Colombian Area, mainly revealed by haplogroup Q-Z780, suggest an entrance in South America prior to 15 kya. During the global constant population size phase, local South American hints of growth were registered by different Q-M848 sub-clades. These expansion events, which started during the Holocene with the improvement of climatic conditions, can be ascribed to multiple cultural changes rather than a steady population growth and a single cohesive culture diffusion as it occurred in Europe. Conclusions: We established and dated a detailed haplogroup Q phylogeny that provides new insights into the geographic distribution of its Eurasian and American branches in modern and ancient samples

Haplotype affinities resolve a major component of goat (<i>Capra hircus</i>) MtDNA D-loop diversity and reveal specific features of the Sardinian stock

Goat mtDNA haplogroup A is a poorly resolved lineage absorbing most of the overall diversity and is found in locations as distant as Eastern Asia and Southern Africa. Its phylogenetic dissection would cast light on an important portion of the spread of goat breeding. The aims of this work were 1) to provide an operational definition of meaningful mtDNA units within haplogroup A, 2) to investigate the mechanisms underlying the maintenance of diversity by considering the modes of selection operated by breeders and 3) to identify the peculiarities of Sardinian mtDNA types. We sequenced the mtDNA D-loop in a large sample of animals (1,591) which represents a non-trivial quota of the entire goat population of Sardinia. We found that Sardinia mirrors a large quota of mtDNA diversity of Western Eurasia in the number of variable sites, their mutational pattern and allele frequency. By using Bayesian analysis, a distance-based tree and a network analysis, we recognized demographically coherent groups of sequences identified by particular subsets of the variable positions. The results showed that this assignment system could be reproduced in other studies, capturing the greatest part of haplotype diversity. We identified haplotype groups overrepresented in Sardinian goats as a result of founder effects. We found that breeders maintain diversity of matrilines most likely through equalization of the reproductive potential. Moreover, the relevant amount of inter-farm mtDNA diversity found does not increase proportionally with distance. Our results illustrate the effects of breeding practices on the composition of maternal gene pool and identify mtDNA types that may be considered in projects aimed at retrieving the maternal component of the oldest breeds of Sardinia.</br

Ancient and modern DNA reveal dynamics of domestication and cross-continental dispersal of the dromedary

Dromedaries have been fundamental to the development of human societies in arid landscapes and for long-distance trade across hostile hot terrains for 3,000 y. Today they continue to be an important livestock resource in marginal agro-ecological zones. However, the history of dromedary domestication and the influence of ancient trading networks on their genetic structure have remained elusive. We combined ancient DNA sequences of wild and early-domesticated dromedary samples from arid regions with nuclear microsatellite and mitochondrial genotype information from 1,083 extant animals collected across the species’ range. We observe little phylogeographic signal in the modern population, indicative of extensive gene flow and virtually affecting all regions except East Africa, where dromedary populations have remained relatively isolated. In agreement with archaeological findings, we identify wild dromedaries from the southeast Arabian Peninsula among the founders of the domestic dromedary gene pool. Approximate Bayesian computations further support the “restocking from the wild” hypothesis, with an initial domestication followed by introgression from individuals from wild, now-extinct populations. Compared with other livestock, which show a long history of gene flow with their wild ancestors, we find a high initial diversity relative to the native distribution of the wild ancestor on the Arabian Peninsula and to the brief coexistence of early-domesticated and wild individuals. This study also demonstrates the potential to retrieve ancient DNA sequences from osseous remains excavated in hot and dry desert environments

GENETIC STRUCTURE AND BIODEMOGRAPHY OF THE RAMA AMERINDIANS FROM THE SOUTHERN CARIBBEAN COAST OF NICARAGUA

This dissertation examines the evolutionary impact of recent historical events on the population structure of the Rama Amerindians who inhabit the southern Caribbean coast of Nicaragua, by analyzing the mitochondrial DNA (mtDNA) polymorphic variants and their biological relationship with, and ancestral divergence from other neighboring groups. Genetic profiles of 265 individuals from seven Rama communities revealed that the majority of individuals belong to haplogroup B2 (71%) or A2 (28%), with the remaining 1% of variation comprised by the maternal lineages C1 and L3. Based on multivariate analyses combined with median-joining networks, AMOVA, tests of selective neutrality and diversity, phylogeography, and surname isonomy analyses, it is proposed that the geographic distribution of the haplogroups among the Rama communities reflects the history of migration of this population after the European incursion into the Caribbean region of Southern Central America following the 16th century. Ethnographic and ethnohistorical accounts of sub-population fissions and subsequent forced migrations are congruent with these results, leading to the conclusion that the disruption of the Rama's traditional way of life led to changes in mortality patterns, reproductive dynamics and epidemiology, which ultimately impacted the genetic variation of this population

Mitochondrial DNA and Y-Chromosome Variation of Eastern Aleut Populations: Implications for the Genetic Structure and Peopling of the Aleutian Archipelago

The Aleuts are the native inhabitants of the Aleutian archipelago off the southwest coast of Alaska and, since Russian contact in 1741, have experienced a series of demographic transitions. This study investigates the impact of historical events on the genetic structure of the Aleut population through analysis of mitochondrial and Y-chromosome DNA variation in five eastern Aleut communities in relation to previous molecular research conducted on communities located further to the west. Results from HVS-I sequencing and Y-SNP and Y-STR typing reveal patterns of variability that exhibit geographic differentiation in an east-west manner. Mitochondrial haplogroups A and D represent the two major maternal lineages observed in the Aleut samples, with haplogroup D more prevalent in the Pribilofs and island groups located to the west. This distribution pattern is likely the result of founder effect related to the forced population resettlements organized by Russian fur traders in the late 18th and early 19th centuries. In the eastern Aleutian Islands and lower Alaska Peninsula, higher frequencies of haplogroup A and its subclades were observed and based on archaeological and phylogeographic evidence may represent the genetic signature of sustained cultural and demic exchange with neighboring Eskimo and Na-Dene groups. The relationship between geography and mtDNA variation is further evident from the highly significant correlation of geographic and genetic distance matrices (r = 0.717) and the decreasing correlogram of spatial autocorrelation values that present a clinal pattern to mtDNA structure. For the Aleut Y-chromosomes, the vast majority were characterized to European haplogroups (approximately 85%), which contrasts the mtDNA picture that reveals only 6.1% non-native matrilines in the eastern region and thus indicating asymmetrical gene flow between European men and Aleut women. Russian paternal lineages are common in the western islands, whereas the predominantly Scandinavian patriline I1a is observed at elevated frequencies in the eastern communities, a consequence of the American purchase of Alaska and the subsequent influx of Scandinavian and US European fishermen into the region. The application of Monmonier's algorithm and genetic surface interpolations for both genetic systems reveal geographic zones of discontinuity at Umnak and Akutan Islands, underscoring the east-west substructure for the Aleut population. Lastly, phylogeographic analysis of mtDNA data and the results of recent ancient DNA studies suggest that subhaplogroup D2 evolved in Beringia and may represent the ancestral gene pool for both Paleo-Eskimos and Aleuts. Overall, this study identifies a significant relationship between geography and genetic variation in the Aleut population, with a distinct substructure along an east-west axis. These regional differences are due to a combination of historical founder effects, male-biased gene flow from European populations, and the peopling of the Aleutian Archipelago during the postglacial period

Melanesian mtDNA Complexity

Melanesian populations are known for their diversity, but it has been hard to grasp the pattern of the variation or its underlying dynamic. Using 1,223 mitochondrial DNA (mtDNA) sequences from hypervariable regions 1 and 2 (HVR1 and HVR2) from 32 populations, we found the among-group variation is structured by island, island size, and also by language affiliation. The more isolated inland Papuan-speaking groups on the largest islands have the greatest distinctions, while shore dwelling populations are considerably less diverse (at the same time, within-group haplotype diversity is less in the most isolated groups). Persistent differences between shore and inland groups in effective population sizes and marital migration rates probably cause these differences. We also add 16 whole sequences to the Melanesian mtDNA phylogenies. We identify the likely origins of a number of the haplogroups and ancient branches in specific islands, point to some ancient mtDNA connections between Near Oceania and Australia, and show additional Holocene connections between Island Southeast Asia/Taiwan and Island Melanesia with branches of haplogroup E. Coalescence estimates based on synonymous transitions in the coding region suggest an initial settlement and expansion in the region at ∼30–50,000 years before present (YBP), and a second important expansion from Island Southeast Asia/Taiwan during the interval ∼3,500–8,000 YBP. However, there are some important variance components in molecular dating that have been overlooked, and the specific nature of ancestral (maternal) Austronesian influence in this region remains unresolved

Mitochondrial genetic characterization of Gujar population living in the Northwest areas of Pakistan

Background: Diversity of communities with specific cultural, ethnic, lingual and geographical backgrounds makes Pakistani society a suitable study subject to unravel the early human migrations, evolutionary history of population having about 18 ethnic groups. Gujars are mostly Indic-speaking nomadic herders with the claims of multiple origins in the sub-continent. Present study was aimed at the determination of maternal lineage of Gujars by mitochondrial DNA analysis.Methods: Total DNA from the human buccal cells was isolated using modified phenol chloroform method. Purified DNA was used for the PCR amplification of mitochondrial Hyper Variable Region 1 and 2 (HVR1 & 2). The nucleotide sequences of amplified PCR products were used to explore the maternal lineage of the Gujar population residing in Northern Pakistan.Results: Haplotypes, allele frequencies and population data of the mitochondrial control region was determined in 73 unrelated individuals belonging to Gujar ethnic group of Northwest areas of Pakistan. Total 46 diverse haplotypes were identified out of which 29 were found unique with (0.9223) genetic diversity and (0.9097) power of discrimination. Haplogroup R was the most frequent (48%) followed by haplogroup M (45%) and N (7%).Conclusion: We found that the Gujar population has multiple maternal gene pool comprising of South Asian, West Eurasian, East Eurasian, Southeast Asian and fractions of Eastern Asian, Eastern Europe and Northern Asian lineages. This study will contribute for the development of mitochondrial DNA database for Pakistani population