Collaborative Research: Social brains and solitary bees: A phylogenetic test of the effect of social behavior on brain evolution across multiple gains and losses of sociality

社会互动如何驱动大脑大小？与其他动物生活在一个社会群体中可能需要更大的大脑来应对维持社会关系的认知挑战。或者，社会群体中的动物可能有更小的大脑，因为社会群体的成员可以一起工作，从而减少每个个体面临的认知挑战。这项研究将测量密切相关的群居蜜蜂和独居蜜蜂的大脑大小。社会合作在蜜蜂中进化了很多次，也失去了很多次：一些孤独的蜜蜂从社会祖先进化而来。 该项目还将测量蜜蜂大脑中与攻击和繁殖有关的神经递质和激素水平。科学家们仍然没有清楚地了解即使是相对简单的大脑差异如何与复杂行为特征的进化相关联。这项研究将使用蜜蜂的小大脑和许多不同的社会和孤独物种之间的多重比较，以调查生活在一个合作的社会群体如何影响大脑。 参与该项目的科学家将通过在他们的实验室实习来指导学生，并将针对初中和高中年龄的学生编写他们的研究出版物版本，这些版本将在网络上免费提供，用于教育和推广。这个项目测试了社会合作的进化导致大脑尺寸增加的假设。这项研究的重点是测量蘑菇体（昆虫大脑的一个区域）的体积变化，以及社会和孤独的蜜蜂大脑的生物胺。研究人员专注于汗蜂（Halictidae），因为这个群体的祖先是孤独的，有三个社会性的进化起源和社会分支内的多个进化损失。此外，许多物种是社会多态性的，表现出社会和孤独的行为。这允许多个遗传独立的社会孤立比较。研究人员专注于蘑菇体体积，因为大脑的这个区域用于学习，记忆和感觉整合。他们测量生物脑胺，因为这些化学物质参与调节攻击性，社会和生殖行为，因此可能参与社会合作的进化。最后，他们测试脑胺水平的变化是否与大脑大小的变化有机械联系，并测量与社会行为相关的胺受体密度的变化。这项工作使用系统发育比较的方法，共聚焦显微镜测量脑体积，高效液相色谱（HPLC）测量胺滴度，和胺反应神经元的抗体染色，以测试如何进化的收益和损失的社会合作影响大脑。这项工作解决了广泛的公众呼吁-大脑进化和合作的问题。作为该项目更广泛影响的一部分，研究人员将与专业编辑合作，为他们的研究创建开放获取的改编版本，用于课堂或其他教育或推广目的。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

How do social interactions drive brain size? Living in a social group with other animals may require a bigger brain in order to deal with the cognitive challenge of maintaining social relationships. Alternatively, animals in social groups may have smaller brains because members of social groups can work together, thus reducing the cognitive challenge faced by each individual. This research will measure brain size in closely related species of social and solitary bees. Social cooperation has evolved many times in bees, and has also been lost many times: some solitary bees evolved from social ancestors. This project will also measure levels of neurotransmitters and hormones in bee brains that are associated with aggression and reproduction. Scientists still do not have a clear understanding of how even relatively simple brain differences are associated with the evolution of complex behavioral traits. This research will use the small brains of bees and the multiple comparisons between many different social and solitary species to investigate how living in a cooperative social group affects the brain. The scientists involved in the project will mentor students through internships in their labs, and will write versions of their research publications aimed at middle- and high-school aged students that will be made freely available on the web for education and outreach. This project tests the hypothesis that the evolution of social cooperation leads to increased brain size. This research focuses on measuring changes in the volume of the mushroom body (an area of the insect brain), and biogenic amines of the brains of social and solitary bees. The researchers focus on the sweat bees (Halictidae) because this group is ancestrally solitary with three evolutionary origins of sociality and multiple evolutionary losses from within the social clades. Also, many species are socially polymorphic, exhibiting both social and solitary behavior. This allows for multiple phylogenetically independent social-solitary comparisons. The researchers focus on mushroom body volume because this area of the brain is used for learning, memory, and sensory integration. They measure biogenic brain amines because these chemicals are involved in regulating aggressive, social, and reproductive behavior, and thus likely involved in the evolution of social cooperation. Lastly, they test whether changes in levels of brain amines are mechanistically linked to changes in brain size, and also measure changes in amine receptor density associated with social behavior. This work uses a phylogenetic comparative approach, confocal microscopy measurements of brain volume, high performance liquid chromatography (HPLC) measurements of amine titers, and antibody staining of amine-reactive neurons to test how evolutionary gains and losses of social cooperation affect the brain. This work addresses issues of broad public appeal - brain evolution and cooperation. As part of the broader impacts of this project, researchers will work with professional editors to create open-access adaptations of their studies for use in classrooms or other educational or outreach purposes. They will also train graduate and undergraduate students across five different institutions.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.