Human-mediated dispersal and breeding reshape global genomic patterns in black soldier flies

Human activities, either intentional or unintentional, have significantly influenced the global distribution and genetic composition of many species. The black soldier fly (Hermetia illucens; BSF) is a species native to North America that has rapidly gained commercial importance due to its bioconversion efficiency, upcycling organic waste into higher-value products. Through human-mediated dispersal associated with trade and insect farming, BSF has been introduced widely across the Old World, including Africa, where both wild and captive populations are now established. Despite its expanding global distribution, the demographic history and genomic consequences of these introductions remain poorly understood, particularly in Africa. This work integrates whole-genome sequencing of newly sampled East African wild and captive populations with publicly available global datasets to characterize patterns of genetic diversity, population structure, and historical spread. Wild populations displayed high genetic diversity and clear geographic structuring, whereas many captive populations showed markedly reduced diversity, elevated inbreeding, and extensive runs of homozygosity. Our results reveal that a substantial fraction of global captive lines can be traced to a narrow lineage of North American origin, while additional captive colonies reflect more recent, independent derivations from local wild populations. These genomic patterns are consistent with demographic processes such as founder effects, genetic drift, and small effective population sizes, rather than coordinated or directional domestication. By resolving the origins and demographic trajectories of African and global BSF populations, this work clarifies the genetic consequences of unstructured breeding and provides a foundation for managing genetic resources in this rapidly expanding insect-farming industry.