Evolution of Social Immunity and Disease Transfer in Honey Bees

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One unique social behaviour of honey bees is how a colony can mitigate infection of larvae without human interventions. These behaviours, which include grooming and destroying infected larvae, are collectively known as hygienic behaviours in honey bees and more generally referred to as social immunity. In the context of managed or farmed honey bee colonies, this is a desirable trait which could help minimize colony losses and potentially help populations rebound. In the proposed work, I will develop population-level and genetic models which can track the spread of hygienic alleles through a network of colonies. Due to the haploid-diploid nature of honey bee mating, as well as the fact that a queen (the only reproductive female within a colony) can be fertilized by up to 20 males, determining the best practices for breeding programs for hygienic behavior can be complex. Through such modeling it will be possible to determine the conditions in which we can realize a consistent proportion of hygienic bees within colonies that will then be self-sustainable. This analysis can then be used to aid and inform best practices for phenotypic or genotypic breeding programs. Moreover, the developed models can be used to explore the two leading hypotheses on the relationship between social immunity and individual immunity. The first is the Social Group Hypothesis which states that the crowded living conditions of social insects can increase vulnerability to pathogens and thus select for individual immunity, despite high metabolic cost. The Regressive Group Hypothesis states that social immunity will relax selection on individual immune function, and it will be maintained at much lower levels in a population. By developing a competition model between two populations, a mutant which exhibits social immunity and a wild type which maintains high individual immunity due to selection pressure, I will be able to provide insights into the conditions under which each hypothesis may be more beneficial, and which may be more common given present conditions. This model will be able to answer fundamental questions about the consequences of sociability in the Hymenoptera in the context of disease. The long-term objective of this research program is to develop a mathematical framework which can be used to study the effects of relaxed selection on the evolution of a species. The training of undergraduate students with strong interdisciplinary skills is integral to this program.