Genomic data reveal a north-south split and introgression history of blood fluke (Schistosoma haematobium) populations from across Africa

Abstract

AbstractThe human parasitic fluke,Schistosoma haematobiumhybridizes with the livestock parasiteS. bovisin the laboratory, but the extent of hybridization in nature is unclear. We analyzed 34.6 million single nucleotide variants in 162 samples from 18 African countries, revealing a sharp genetic discontinuity between northern and southernS. haematobium. We found no evidence for recent hybridization. Instead the data reveal admixture events that occurred 257-879 generations ago in northernS. haematobiumpopulations. Fifteen introgressedS. bovisgenes are approaching fixation in northernS. haematobiumwith four genes potentially driving adaptation. We identified 19 regions that were resistant to introgression; these were enriched on the sex chromosomes. These results (i) demonstrate strong barriers to gene flow between these species, (ii) indicate that hybridization may be less common than currently envisaged, but (iii) reveal profound genomic consequences of interspecific hybridization between schistosomes of medical and veterinary importance.