Genetic ancestry, admixture, and population structure in rural Dominica.

The Caribbean is a genetically diverse region with heterogeneous admixture compositions influenced by local island ecologies, migrations, colonial conflicts, and demographic histories. The Commonwealth of Dominica is a mountainous island in the Lesser Antilles historically known to harbor communities with unique patterns of migration, mixture, and isolation. This community-based population genetic study adds biological evidence to inform post-colonial narrative histories in a Dominican horticultural village. High density single nucleotide polymorphism data paired with a previously compiled genealogy provide the first genome-wide insights on genetic ancestry and population structure in Dominica. We assessed family-based clustering, inferred global ancestry, and dated recent admixture by implementing the fastSTRUCTURE clustering algorithm, modeling graph-based migration with TreeMix, assessing patterns of linkage disequilibrium decay with ALDER, and visualizing data from Dominica with Human Genome Diversity Panel references. These analyses distinguish family-based genetic structure from variation in African, European, and indigenous Amerindian admixture proportions, and analyses of linkage disequilibrium decay estimate admixture dates 5-6 generations (~160 years) ago. African ancestry accounts for the largest mixture components, followed by European and then indigenous components; however, our global ancestry inferences are consistent with previous mitochondrial, Y chromosome, and ancestry marker data from Dominica that show uniquely higher proportions of indigenous ancestry and lower proportions of African ancestry relative to known admixture in other French- and English-speaking Caribbean islands. Our genetic results support local narratives about the community's history and founding, which indicate that newly emancipated people settled in the steep, dense vegetation along Dominica's eastern coast in the mid-19th century. Strong genetic signals of post-colonial admixture and family-based structure highlight the localized impacts of colonial forces and island ecologies in this region, and more data from other groups are needed to more broadly inform on Dominica's complex history and present diversity.

Anthropometric heritability and child growth in a Caribbean village: A quantitative genetic analysis of longitudinal height, weight, and body mass index in Bwa Mawego, Dominica.

OBJECTIVES: Body size and composition vary widely among individuals and populations, and long-term research in diverse contexts informs our understanding of genetic, cultural, and environmental impacts on this variation. We analyze longitudinal measures of height, weight, and body mass index (BMI) from a Caribbean village, estimating the extent to which these anthropometrics are shaped by genetic variance in a small-scale population of mixed ancestry. MATERIALS AND METHODS: Longitudinal data from a traditionally horticultural village in Dominica document height and weight in a non-Western population that is transitioning to increasingly Westernized lifestyles, and an 11-generation pedigree enables us to estimate the proportions of phenotypic variation in height, weight, and BMI attributed to genetic variation. We assess within-individual variation across growth curves as well as heritabilities of these traits for 260 individuals using Bayesian variance component estimation. RESULTS: Age, sex, and secular trends account for the majority of anthropometric variation in these longitudinal data. Independent of age, sex, and secular trends, our analyses show high repeatabilities for the remaining variation in height, weight, and BMI growth curves (>0.75), and moderate heritabilities (h2height = 0.68, h2weight = 0.64, h2BMI = 0.49) reveal clear genetic signals that account for large proportions of the variation in body size observed between families. Secular trends show increases of 6.5% in height and 16.0% in weight from 1997 to 2017. DISCUSSION: This horticultural Caribbean population has transitioned to include more Westernized foods and technologies over the decades captured in this analysis. BMI varies widely between individuals and is significantly shaped by genetic variation, warranting future exploration with other physiological correlates and associated genetic variants.