Patterns of Genetic Diversity and Mating Systems in a Mass-Reared Black Soldier Fly Colony

SIMPLE SUMMARY: With a growing human population, global climate change and diminishing natural resources, the need for sustainable agricultural systems is evident. Insect farming has been shown to be an envi-ronmentally friendly alternative to conventional livestock farming. The black soldier fly (BSF) is a species of interest because the larvae are effective bioremedial agents, feeding on organic waste and converting it to usable animal derived products that have a similar nutrient profile to conventional feedstuffs like soy and fishmeal. This creates an opportunity for renewable food production systems. Managing genetic diversity in commercial insect populations is important for the long-term viability and productivity of the colony to mitigate any negative effects of inbreeding. In this study we in-vestigated the effects population dynamics and breeding behaviour on the genetic health of a mass reared BSF colony. The results suggest significant loss in genetic diversity and rapid divergence of captive populations from ancestral wild ones. The study also gives the first evidence for multiple paternity in BSF. The results will contribute to establishing effective genetic management strategies for BSF farming, ensuring long term sustainability of a new industry ABSTRACT: The black soldier fly (BSF), Hermetia illucens, is a promising candidate for the emerging insect farming industry with favourable characteristics for both bioremediation and production of animal delivered nutritive and industrial compounds. The genetic management of commercial colonies will become increasingly important for the sustainability of the industry. However, r-selected life history traits of insects pose challenges to conventional animal husbandry and breeding approaches. In this study, the long-term genetic effects of mass-rearing were evaluated as well as mating systems in the species to establish factors that might influence genetic diversity, and by implication fitness and productivity in commercial colonies. Population genetic parameters, based on microsatellite markers, were estimated and compared amongst two temporal wild sampling populations and four generations (F28, F48, F52, and F62) of a mass-reared colony. Furthermore, genetic relationships amongst mate pairs were evaluated and parentage analysis was performed to determine the oc-currence of preferential mate choice and multiple paternity. The mass-reared colony showed a reduction in genetic diversity and evidence for inbreeding with significant successive generational genetic differentiation from the wild progenitor population. Population-level analysis also gave the first tentative evidence of positive assortative mating and genetic polyandry in BSF. The homoge-neity of the mass-reared colony seems to result from a dual action caused by small effective popu-lation size and increased homozygosity due to positive assortative mating. However, the high ge-netic diversity in the wild and a polyandrous mating system might suggest the possible restoration of diversity in mass-reared colonies through augmentation with the wild population.