Ito Koichi, Higginson Andrew
Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QG, UK.
Philos Trans R Soc Lond B Biol Sci. 2025 Mar 20;380(1922):20230264. doi: 10.1098/rstb.2023.0264.
An important advantage to sociality is division of labour, which is often associated with specialization of group members, such as the polymorphic subcastes of ant workers. Given this advantage, it is puzzling that many social groups do not show clear specialization. Among ants, workers of closely related species have one, two or even three polymorphisms. The degree of specialism of asocial animals depends on environmental variability because specialists will perform poorly in some conditions. Here, we use a numeric model to consider whether the magnitude and type of environmental variability can help to explain the diversity of specialism in cooperative groups. By finding the optimal distribution of group members along a single dimension of specialization for two tasks, we predict when groups should be composed of specialists, generalists, both of these (trimodal) or moderate specialists. Generalism is predicted more when environments are unstable and when task importance-rather than demand-varies but depends on the likelihood that the group can complete all tasks in the range of experienced conditions. The benefit of sociality is strongest in invariable environments and there is selection for redundancy in the workforce, which may explain the widely observed inactivity in social insects.This article is part of the theme issue 'Division of labour as key driver of social evolution'.
社会性的一个重要优势是劳动分工，这通常与群体成员的专业化相关联，比如蚂蚁工蚁的多态性亚等级。鉴于这一优势，许多社会群体并未表现出明显的专业化现象就令人费解了。在蚂蚁中，亲缘关系相近的物种的工蚁具有一种、两种甚至三种多态性。非社会性动物的专业化程度取决于环境变异性，因为专家型个体在某些条件下表现不佳。在此，我们使用一个数值模型来探讨环境变异性的程度和类型是否有助于解释合作群体中专业化的多样性。通过找到群体成员在针对两项任务的单一专业化维度上的最优分布，我们预测群体何时应由专家型个体、通才型个体、兼具两者（三峰型）或适度专家型个体组成。当环境不稳定且任务重要性（而非需求）发生变化但取决于群体在经历的条件范围内完成所有任务的可能性时，预测通才型个体更为常见。社会性的益处在不变的环境中最为显著，并且存在对劳动力冗余的选择，这或许可以解释在社会性昆虫中广泛观察到的不活动现象。本文是主题为“劳动分工是社会进化的关键驱动力”的一部分。
