DISSERTATION RESEARCH: Does resource limitation promote cooperation? Nutrition restriction and social cohesion in insect societies

为什么合作会在生物体群体中进化，以及合作如何在生物体群体中持续存在，这是生物学家仍在努力回答的一个问题。这项研究将调查有限的营养是否导致并继续促进自然界最大的合作者之一--群居昆虫--的合作增加。该项目将整合行为、遗传和生理研究，以调查营养限制如何影响两个物种的合作--一个是简单社会的物种(纸蜂)，另一个是复杂社会的物种(蜜蜂)。在这两种生物的实验群体中，发育中的工人的饮食将发生变化，一些人将经历营养压力，另一些人将获得正常的健康饮食。当这些工作人员成年后，研究人员将检查他们的合作行为(或多或少地攻击其他工作人员，照顾女王，抚养他们的姐妹)，以检验营养资源减少会促进合作的假设。通过比较简单和复杂的群居昆虫社会，这项研究将检验资源限制是否可能成为合作演变的一个总主题。这项研究还将通过分析饥饿和非饥饿个体的卵巢大小、脂肪以及生殖和营养相关基因的活动，来研究营养如何通过生理和基因表达影响行为差异。研究将与昆虫和进化教育相结合，通过公开演讲和免费提供的有趣的互联网内容，以及不同背景的本科生和研究助理直接参与研究活动。在社会昆虫群体中，合作的一个基本形式是女王(群体中唯一的生殖者)和她的工蚁(女王的女儿)之间的合作。工蜂对蜂后的反应各不相同，这一行为对蜂群的社会凝聚力至关重要。营养压力大的工蚁对蜂王高度敏感，而高营养饮食的工蜂对蜂王的敏感度较低。研究人员将通过研究两种社会性昆虫--蜜蜂和纸蜂--的营养和生殖生理学要素以及相关的分子途径，来研究营养和合作之间潜在联系的机制是否在进化上是保守的。他们将在蜜蜂身上扩展这项先前的工作，以解决营养应激导致的蜂后反应性增加是否是与生殖和营养信号相关的保守基因调控发生变化所致。其次，研究人员将利用原始的社会纸黄蜂Polistes metricus开始研究这种模式的普遍性和进化保守性。Polistes的工蚁将受到营养限制，并将记录行为观察，以测试这是否会导致鸟巢工蚁的社会凝聚力更高。研究人员还将测量这些变化如何影响卵巢发育，以及与生殖和营养信号相关的基因表达的变化。如果营养受限的Polistes工作者表现出更高的合作行为，那么营养压力和合作之间的联系可能代表了昆虫社会中调节社会凝聚力的一种保守机制。当营养缺乏时，合作可能具有战略意义，而营养压力与合作之间的联系可能是社会进化中的一个共同主题。

Why cooperation evolves and how it persists in groups of organisms is a question that biologists are still working to answer. This research will investigate if limited nutrition has led to and continues to promote increased cooperation in one of nature's greatest cooperators: the social insects. The project will integrate behavioral, genetic, and physiological research to investigate how nutrition limitation affects cooperation in two species - one with simple societies (paper wasps) and one with complex societies (honey bees). In experimental colonies of both these organisms, the diets of developing workers will be altered such that some individuals will experience nutritional stress and others will receive normal healthy diets. When these workers reach adulthood, the researchers will examine how cooperatively they behave (more or less aggression toward other workers, tending the queen, raising their sisters), testing the hypothesis that decreased nutritional resources promote increased cooperation. By comparing simple and complex social insect societies, this research will examine whether resource limitation could be a general theme in the evolution of cooperation. By analyzing ovary size, fattiness, and the activity of reproduction and nutrition related genes in starved and un-starved individuals, this research will also examine how nutrition can influence differences in behavior through physiology and gene expression. Research will be paired with insect and evolution education outreach via public talks and freely available and entertaining internet content, as well as direct participation in research activities by undergraduates and research assistants of diverse backgrounds.An essential form of cooperation in a social insect colony is between the queen (the sole reproductive in the colony) and her workers (the queen's daughters). Worker honey bees vary in their responsiveness to the queen a behavior that is essential to colony social cohesion. Nutritionally stressed workers exhibit a high sensitivity to the queen, and workers with high nutrition diets exhibit a low sensitivity. The researchers will investigate if mechanisms underlying the link between nutrition and cooperation are evolutionarily conserved by studying elements of nutritional and reproductive physiology and associated molecular pathways in two eusocial insects, honey bees and paper wasps. They will expand this prior work on honey bees to address whether nutritional stress-induced increases in queen responsiveness are underlain by changes in the regulation of conserved genes related to reproduction and nutrient signaling. Second, the researchers will utilize the primitively social paper wasp Polistes metricus to begin to address the generality and evolutionary conservation of this pattern. Polistes workers will be nutritionally restricted and behavioral observations will be recorded to test whether this leads to higher social cohesion of workers on the nest. The researchers will also measure how these changes affect ovary development and changes in the expression of genes associated with reproduction and nutrient signaling. If nutritionally restricted Polistes workers exhibit higher cooperative behavior, then the connection between nutritional stress and cooperation may represent a conserved mechanism regulating social cohesion in insect societies. Cooperation may be strategic when nutrition is scarce, and the link between nutritional stress and cooperation may be a common theme in social evolution.