Supplementary Material for: Linking Colony Size with Foraging Behavior and Brain Investment in Odorous Ants (Formicidae: Dolichoderinae)

Superorganisms represent a unique level of biological organization in which the phenotype of the reproductive unit, the colony, results from traits expressed at the level of individual workers. Because body size scaling has important consequences for cell diversity and system complexity in solitary organisms, colony size is a trait of particular interest in superorganism evolution. In some instances, division of labor and worker polymorphism scale with colony size, but in general little is known about how colony size drives differences in individual-level behavior or neural traits. Ants represent the greatest diversity of superorganisms and provide a manner of natural experiment to test trends in trait evolution across multiple instances of colony size expansion. In this study, we control for environmental differences and worker size polymorphism to test if colony size correlates with measures of foraging behavior and brain size in dolichoderine ants. We present data from 3 species ranked by colony size. Our results suggest colony size correlates with measures of exploratory behavior and brain investment, with small-colony ants showing higher exploratory drive and faster exploration rate than the larger colony species, and greater relative investment in the primary olfactory brain region, the antennal lobe, than the larger colony species.超有机体（Superorganisms）代表了一种独特的生物组织层级，其中繁殖单元——蚁群——的表型源自工蚁个体所表达的性状。由于在独居生物中，体型缩放对细胞多样性与系统复杂度具有重要影响，因此蚁群规模是超有机体演化中尤为受关注的性状。在部分案例中，劳动分工与工蚁多态性会随蚁群规模发生缩放，但总体而言，学界对蚁群规模如何驱动个体行为或神经性状的差异仍所知甚少。蚂蚁拥有最为多样的超有机体类群，为跨多个蚁群规模扩张的案例检验性状演化趋势提供了天然实验模型。本研究中，我们控制了环境差异与工蚁体型多态性变量，以检验臭蚁亚科（Dolichoderinae）蚂蚁的蚁群规模是否与觅食行为指标及脑容量存在关联。我们提供了按蚁群规模排序的3个物种的相关数据。研究结果表明，蚁群规模与探索行为指标及脑投资水平存在关联：相较于大蚁群物种，小蚁群蚂蚁展现出更强的探索驱动力与更快的探索速度，且其初级嗅觉脑区——触角叶（antennal lobe）——的相对投资更高。