Social and ecological drivers of life history evolution in wild bees

所有生物体都必须平衡在基本功能上的能量投资，如健康和生殖，这通常会导致一生中的权衡。然而，这些基本的生活规则似乎并不适用于群居的昆虫。例如，一些蚂蚁、蜜蜂和白蚁的女王可以活几年甚至几十年，尽管产卵数千或数十万，但它们不育的姐妹和女儿只活几天或几周。这种与其他普遍的生活史权衡的巨大背离背后的机制尚不清楚，部分原因是所研究的物种类型的限制。这个项目将集中在野蜂身上，以确定社会性的变化如何影响蜜蜂如何平衡在繁殖、健康和长寿方面的投资。通过扩大分析的广度(物种数量)和深度(关键物种内的生态相关实验)，该项目将为蜜蜂如何在不断变化的环境条件下优化适应能力提供独特的见解，这对于在传粉者减少的情况下缓解与全球粮食安全相关的问题至关重要。该项目将为学生(本科生和研究生)和一名博士后研究员提供培训和指导。培训将专门针对来自地区校园的美洲原住民学生，通过暑期研究项目和奖学金的指导来扩大对STEM的参与。这项研究产生的结果将用于开发名为基因与行为的高年级/研究生课程中的指导性体验式学习模块。生活史理论一直是通过进化框架解释行为和生态变化的指南，但社会性昆虫似乎打破了规则，逃离了繁殖力和寿命之间的经典权衡。这表明，社会进化影响着生活史的进化，从根本上改变了生活史策略如何变化的基本限制。该团队将在三组实验中调查野生蜜蜂如何投资于生活史特征(免疫、繁殖)，作为生态和社会环境变化的函数。首先，将对多种蜜蜂物种的内部和外部免疫进行测试，以测试优势性的演变如何塑造免疫功能投资的替代假说。其次，重点将转移到一种兼职的群居蜜蜂(Megalopta Genalis)上，它允许在相同的生态条件下直接比较独居和群居个体的生活史权衡。比较独居雌性和群居雌性在后代出现前后三个组织的免疫反应、氧化应激和基因表达谱，将利用能量储备的自然差异来了解获取资源如何影响对生存(即免疫、衰老、死亡风险)和繁殖的投资，以及支撑这些特征的分子途径。最后一组实验将通过实验将工蚁从群居的膝毛虫巢中移走，并测量它们对蜂王存活、繁殖及其潜在机制的影响，从而直接检验这些发现。这些活动将确定社会进化影响生活史进化的机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

All organisms must balance energetic investment in essential functions, such as health and reproduction, and this typically leads to trade-offs over the course of a lifetime. However, these basic rules of life do not seem to apply to insects that live in social groups. For example, queens of some ants, bees, and termites can live for years or even decades, despite laying thousands or hundreds of thousands of eggs, but their sterile sisters and daughters live for just days or weeks. The mechanisms underlying this drastic departure from otherwise universal life history trade-offs are unknown, in part due to limitations in the types of species that have been studied. This project will focus on wild bees to determine how variation in sociality influences how bees balance investment in reproduction, health, and longevity. By expanding the breadth (number of species) and depth (ecologically relevant experiments within a key species) of analysis, the project will provide unique insights into how bees optimize fitness under changing environmental conditions, which is critical for mitigating issues related to global food security in the face of pollinator decline. The project will provide training and mentorship for students (undergraduate and graduate) and a postdoctoral researcher. Training will specifically target Native American students from a regional campus to broaden participation in STEM through mentorship in a summer research program and fellowship. Results generated from the research will be used to develop guided experiential learning modules in an upper division/graduate course called Genes and Behavior. Life history theory has been a guidepost for interpreting variation in behavior and ecology through an evolutionary framework, but social insects seem to break the rules by escaping classic tradeoffs between fecundity and longevity. This suggests that social evolution influences life history evolution, fundamentally altering what seem to be otherwise basic constraints in how life history strategies can vary. The team will investigate how wild bees invest in life history traits (immunity, reproduction) as a function of variation in the ecological and social environment in three sets of experiments. First, internal and external immunity will be assayed in multiple bee species to test alternative hypotheses for how the evolution of eusociality has shaped investment in immune function. Second, the focus will shift to a facultatively eusocial bee (Megalopta genalis) that allows direct comparison of life history tradeoffs in solitary and social individuals under the same ecological conditions. Comparing immune response, oxidative stress, and gene expression profiles in three tissues between solitary and social females before and after offspring emergence will take advantage of natural differences in energy reserves to see how access to resources influences investment in survival (i.e., immunity, senescence, mortality risk) and reproduction, as well as the molecular pathways underpinning these traits. A final set of experiments will test these findings directly by experimentally removing the workers from social M. genalis nests and measuring the effects on queen survival, reproduction, and their underlying mechanisms. These activities will identify the mechanisms by which social evolution influences life history evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.