The definition of eusociality

TLDR

Eusociality is defined by the presence of castes that become irreversibly behaviorally distinct before reproductive maturity, with helping by less‑reproductive castes and either totipotency of the reproductive caste (facultative) or none (obligate), and cooperative breeding societies are hypothesized to be semisocial or quasisocial, requiring empirical study. The study aims to refine definitions of eusociality and related social systems, defining cooperative breeding as alloparental care without castes and proposing semisocial and quasisocial categories for further empirical testing. The authors establish precise definitions for eusociality and cooperative breeding, delineating castes, helping behavior, totipotency, and the two cooperative breeding categories. These definitions conceptually unify arthropod and vertebrate sociality studies.

Abstract

We describe more precise definitions for the term "eusociality" and other social systems. Our criterion for eusociality is the presence of castes, which are groups of individuals that become irreversibly behaviorally distinct at some point prior to reproductive maturity. Eusocial societies are characterized by two traits: (1) helping by individuals of the less-reproductive caste, and (2) either behavioral totipotency of only the more reproductive caste (facultative eusociality) or totipotency of neither caste (obligate eusociality). We define "cooperative breeding" as alloparental care without castes. Cooperatively breeding societies may comprise two types, semisocial (distribution of lifetime reproductive success bimodal), and quasisocial (distribution of lifetime reproductive success unimodal), but this hypothesis requires empirical analysis. Our definitions conceptually unify studies of arthropod and vertebrate sociality.