Paternal lineages signal distinct genetic contributions from British Loyalists and continental Africans among different Bahamian islands

Exploring the legacy of African and Indigenous Caribbean admixture in Puerto Rico

OBJECTIVES

From an anthropological genetic perspective, little is known about the ethnogenesis of African descendants in Puerto Rico. Furthermore, historical interactions between Indigenous Caribbean and African descendant peoples that may be reflected in the ancestry of contemporary populations are understudied. Given this dearth of genetic research and the precedence for Afro-Indigenous interactions documented by historical, archeological, and other lines of evidence, we sought to assess the biogeographic origins of African descendant Puerto Ricans and to query the potential for Indigenous ancestry within this community.

MATERIALS AND METHODS

Saliva samples were collected from 58 self-identified African descendant Puerto Ricans residing in Puerto Rico. We sequenced whole mitochondrial genomes and genotyped Y chromosome haplogroups for each male individual (n = 25). Summary statistics, comparative analyses, and network analysis were used to assess diversity and variation in haplogroup distribution between the sample and comparative populations.

RESULTS

As indicated by mitochondrial haplogroups, 66% had African, 5% had European, and 29% had Indigenous American matrilines. Along the Y chromosome, 52% had African, 28% had Western European, 16% had Eurasian, and, notably, 4% had Indigenous American patrilines. Both mitochondrial and Y chromosome haplogroup frequencies were significantly different from several comparative populations.

DISCUSSION

Biogeographic origins are consistent with historical accounts of African, Indigenous American, and European ancestry. However, this first report of Indigenous American paternal ancestry in Puerto Rico suggests distinctive features within African descendant communities on the island. Future studies expanding sampling and incorporating higher resolution genetic markers are necessary to more fully understand African descendant history in Puerto Rico.

Y Haplogroup Diversity of the Dominican Republic: Reconstructing the Effect of the European Colonization and the Trans-Atlantic Slave Trades

The Dominican Republic is one of the two countries on the Hispaniola island, which is part of the Antilles. Hispaniola was affected by the European colonization and massive deportation of African slaves since the XVI century and these events heavily shaped the genetic composition of the present-day population. To shed light about the effect of the European rules, we analyzed 92 single nucleotide polymorphisms on the Y chromosome in 182 Dominican individuals from three different locations. The Dominican Y haplogroup composition was characterized by an excess of northern African/European lineages (59%), followed by the African clades (38%), whereas the Native-American lineages were rare (3%). The comparison with the mitochondrial DNA variability, dominated by African clades, revealed a sex-biased admixture pattern, in line with the colonial society dominated by European men. When other Caribbean and non-Caribbean former colonies were also considered, we noted a difference between territories under a Spanish rule (like the Dominican Republic) and British/French rule, with the former characterized by an excess of European Y lineages reflecting the more permissive Iberian legislation about mixed people and slavery. Finally, we analyzed the distribution in Africa of the Dominican lineages with a putative African origin, mainly focusing on central and western Africa, which were the main sources of African slaves. We found that most (83%) of the African lineages observed in Santo Domingo have a central African ancestry, suggesting that most of the slaves were deported from regions.

The peopling of the African continent and the diaspora into the new world

Africa is the birthplace of anatomically modern humans, and is the geographic origin of human migration across the globe within the last 100,000 years. The history of African populations has consisted of a number of demographic events that have influenced patterns of genetic and phenotypic variation across the continent. With the increasing amount of genomic data and corresponding developments in computational methods, researchers are able to explore long-standing evolutionary questions, expanding our understanding of human history within and outside of Africa. This review will summarize some of the recent findings regarding African demographic history, including the African Diaspora, and will briefly explore their implications for disease susceptibility in populations of African descent.

An anthropological genetic perspective on Creolization in the Anglophone Caribbean

Variable socio-cultural influences developed in the colonial Caribbean as a result of competing European hegemonic rule. In this study, we examine how colonial regulations regarding social hierarchies and mate choice worked to influence the genetic landscape of contemporary African Caribbean populations. To this end, 420 individuals from Dominica, Grenada, St. Kitts, St. Lucia, St. Thomas, St. Vincent, Jamaica, and Trinidad were genotyped for 105 autosomal ancestry informative markers. Based on these data, population substructure and admixture were assessed using an exact test, a model-based clustering method, and principal components analysis. On average, individual admixture estimates of the pooled African Caribbean sample were 77% (SD ± 18%) West African, 15% (SD ± 15%) European, and 7.7% (SD ± 8%) Native American. In general, ancestry estimates were significantly different between Dominica and all other islands. Genetic structure analyses indicated subdivision into two subpopulations on most islands. Finally, unlike all of the other Caribbean populations that clustered adjacent to African populations, the Dominican population was more intermediate between the three parental groups in the principal components plot. As a result of the significant French influence throughout Dominican history, Dominica did not have the same cultural influences that typified other Anglophone colonies. Consequently, there were different social hierarchies and resulting mate choices on Dominica compared with the other considered islands. This study highlights the complex socio-cultural history of a broad region of the Caribbean and attests to the interplay between social and biological factors in shaping the genetic diversity present in present-day communities.

Genetic genealogy comes of age: perspectives on the use of deep-rooted pedigrees in human population genetics

In this article, we promote the implementation of extensive genealogical data in population genetic studies. Genealogical records can provide valuable information on the origin of DNA donors in a population genetic study, going beyond the commonly collected data such as residence, birthplace, language, and self-reported ethnicity. Recent studies demonstrated that extended genealogical data added to surname analysis can be crucial to detect signals of (past) population stratification and to interpret the population structure in a more objective manner. Moreover, when in-depth pedigree data are combined with haploid markers, it is even possible to disentangle signals of temporal differentiation within a population genetic structure during the last centuries. Obtaining genealogical data for all DNA donors in a population genetic study is a labor-intensive task but the vastly growing (genetic) genealogical databases, due to the broad interest of the public, are making this job more time-efficient if there is a guarantee for sufficient data quality. At the end, we discuss the advantages and pitfalls of using genealogy within sampling campaigns and we provide guidelines for future population genetic studies.

Y-chromosome and surname analysis of the native islanders of San Andrés and Providencia (Colombia)

The Archipelago of San Andrés and Providencia is a Colombian Department in the western waters of the Caribbean Sea. Most of its inhabitants belong to the African-Colombian group known as raizal. This group has unique cultural traits that are derived from centuries of admixture of the primarily African slaves and European colonists. Currently, not much is known about the genetic profile of this population. Therefore, this study aimed to determine the Y-chromosome STR genetic structure and relationship to previously published reference populations. A total of 54 natives from the islands were selected based on the genealogical criterion of having three generations of ancestors born in the Archipelago. Seventeen Y-STRs were analyzed, supplemented by information on the first surname inherited. The genetic substructure hypothesis in the studied islands was tested, and no significant differences were found (p>0.05). Y-chromosome haplogroups were predicted, and E1b1a and R1b were the most commonly found haplogroups. They account for more than 80% of the sample. The E1b1a and R1ba haplogroups are common in the African and European populations, respectively. For comparative genetic analysis, genetic distances were calculated with respect to populations from the Caribbean, Colombia, Europe and Africa. We found greater similarity between the African and Caribbean populations. The surname analysis demonstrated that most of the time, the "raizales" with the same surname also shared the same Y-STR haplotype. This suggests that some kinship relationship exists between participants with the same surname, which was confirmed by the haplotype diversity levels found in the studied islands.

Y-STR diversity and sex-biased gene flow among Caribbean populations

In the present study, we report, for the first time, the allele and haplotype frequencies of 17 Y-STR (Y-filer) loci in the populations of Haiti, Jamaica and the Bahamas (Abaco, Eleuthera, Exuma, Grand Bahama, Long Island and New Providence). This investigation was undertaken to assess the paternal genetic structure of the abovementioned Caribbean islands. A total of 607 different haplotypes were identified among the 691 males examined, of which 537 (88.5%) were unique. Haplotype diversities (HD) ranged from 0.989 in Long Island to 1.000 in Grand Bahama, with limited haplotype sharing observed among these Caribbean collections. Discriminatory capacity (DC) values were also high, ranging from 79.1% to 100% in Long Island and Grand Bahama, respectively, illustrating the capacity of this set of markers to differentiate between patrilineal related individuals within each population. Phylogenetic comparison of the Bahamian, Haitian and Jamaican groups with available African, European, East Asian and Native American populations reveals strong genetic ties with the continental African collections, a finding that corroborates our earlier work using autosomal STR and Y-chromosome binary markers. In addition, various degrees of sex-biased gene flow exhibiting disproportionately higher European paternal (as compared to autosomal) influences were detected in all Caribbean islands genotyped except for Abaco and Eleuthera. We attribute the presence or absence of asymmetric gene flow to unique, island specific demographic events and family structures.

Molecular dissection of the basal clades in the human Y chromosome phylogenetic tree

One hundred and forty-six previously detected mutations were more precisely positioned in the human Y chromosome phylogeny by the analysis of 51 representative Y chromosome haplogroups and the use of 59 mutations from literature. Twenty-two new mutations were also described and incorporated in the revised phylogeny. This analysis made it possible to identify new haplogroups and to resolve a deep trifurcation within haplogroup B2. Our data provide a highly resolved branching in the African-specific portion of the Y tree and support the hypothesis of an origin in the north-western quadrant of the African continent for the human MSY diversity.