Evolution of Social Immunity and Disease Transfer in Honey Bees

蜜蜂的一种独特的社会行为是，一个蜂群如何在没有人类干预的情况下减轻对幼虫的感染。这些行为包括梳理和摧毁受感染的幼虫，统称为蜜蜂的卫生行为，更广泛地被称为社会免疫。在管理或养殖的蜂群中，这是一个可取的特征，可以帮助将蜂群损失降至最低，并有可能帮助蜂群反弹。 在这项拟议的工作中，我将开发种群水平和遗传模型，以跟踪卫生等位基因通过群体网络的传播。由于蜜蜂交配的单倍体-二倍体性质，以及一个蜂王(一个蜂群中唯一有生殖能力的雌性蜜蜂)可以与多达20只雄性蜜蜂受精的事实，确定卫生行为繁殖计划的最佳实践可能是复杂的。通过这样的建模，我们将有可能确定在什么条件下我们可以在蜂群中实现一致的卫生蜜蜂比例，然后这些蜜蜂将是自我维持的。然后，这种分析可以用来帮助和告知表型或遗传型育种计划的最佳做法。 此外，所开发的模型可以用来探索关于社会免疫和个人免疫之间关系的两个主要假说。第一种是社会群体假说，该假说认为，尽管代谢成本很高，但群居昆虫拥挤的生存条件会增加对病原体的易感性，从而选择个体免疫。退化组假说指出，社会免疫将放松对个体免疫功能的选择，并将其维持在一个种群中的较低水平。通过建立两个种群之间的竞争模型，一个突变体表现出社会免疫力，一个野生型由于选择压力而保持较高的个体免疫力，我将能够提供对每个假设可能更有利的条件的洞察，以及在目前条件下可能更常见的条件。这个模型将能够回答有关膜翅目在疾病背景下的社会性后果的基本问题。 这项研究计划的长期目标是开发一个数学框架，用于研究放松选择对物种进化的影响。 对具有较强跨学科技能的本科生的培训是该项目不可或缺的一部分。

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.