Abstract
BackgroundBioko is one of the few islands that exist around Africa, the most genetically diverse continent on the planet. The native Bantu-speaking inhabitants of Bioko, the Bubi, are believed to have colonized the island about 2000 years ago. Here, we sequenced the genome of thirteen Bubi individuals at high coverage and analysed their sequences in comparison to mainland populations from the Gulf of Guinea.ResultsWe found that, genetically, the closest mainland population to the Bubi are Bantu-speaking groups from Angola instead the geographically closer groups from Cameroon. The Bubi possess a lower proportion of rainforest hunter-gatherer (RHG) ancestry than most other Bantu-speaking groups. However, their RHG component most likely came from the same source and could have reached them by gene flow from the mainland after island settlement. By studying identity by descent (IBD) genomic blocks and runs of homozygosity (ROHs), we found evidence for a significant level of genetic isolation among the Bubi, isolation that can be attributed to the island effect. Additionally, as this population is known to have one of the highest malaria incidence rates in the world we analysed their genome for malaria-resistant alleles. However, we were unable to detect any specific selective sweeps related to this disease.ConclusionsBy describing their dispersal to the Atlantic islands, the genomic characterization of the Bubi contributes to the understanding of the margins of the massive Bantu migration that shaped all Sub-Saharan African populations.
Highlights
Bioko is one of the few islands that exist around Africa, the most genetically diverse continent on the planet
To examine if this clustering reveals the presence of population substructure, we have used the USCS liftover [28] to convert the chimpanzee reference sequence (Pan troglodytes 3.0 assembly, GCA_000001515.5) to human coordinates in 546,558 single nucleotide polymorphisms (SNPs) of our dataset
We have found that the Bubi show the highest levels of shared ancestry with the Western African populations, which do not overlap with other populations when the comparison is established with rainforest hunter-gatherer (RHG) components
Summary
Bioko is one of the few islands that exist around Africa, the most genetically diverse continent on the planet. The native Bantu-speaking inhabitants of Bioko, the Bubi, are believed to have colonized the island about 2000 years ago. Of the few islands located in Atlantic Africa, four of them are found within the Gulf of Guinea (Fig. 1a). Bioko is the largest of these islands, with a total area of 2017 km (Fig. 1b). It is located 32 km offshore of Cameroon but constitutes the northernmost part of Equatorial Guinea, a former Spanish colony. Since the British explorer Richard Francis Burton visited the island ( called Fernando Poo) in 1874 [5], ethnographers generally considered the Bubi to be the original settlers of Bioko. It is currently accepted that the Bubi agriculturalists arrived from the mainland in dugout canoes about 2000 years ago during the Late
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