Collective personalities: present knowledge and new frontiers

Collective personalities refer to temporally consistent behavioral differences between distinct social groups. This phenomenon is a ubiquitous and key feature of social groups in nature, as virtually every study conducted to date has documented repeatable between-group differences in collective behavior, and has revealed ongoing selection on these traits in both the laboratory and field environments. Five years ago, foundational reviews by Bengston and Jandt pioneered this topic and delimited the present knowledge on collective personality. Here, we update these reviews by summarizing the recent works conducted in the field’s most prominent model systems: social spiders and eusocial insects. After presenting how these recent works helped scientists to better understand the determinants of collective personality, we used a trait-by-trait format to compare and contrast the results and thematic trends obtained in these taxa on 10 major aspects of collective personality: division of labor, foraging, exploration, boldness, defensive behavior, aggressiveness, decision-making, cognition, learning, and nest construction. We then discuss why similarities and dissimilarities in these results open the door to applying numerous theories developed in evolutionary behavioral ecology for individual traits (e.g., life history theory, game theory, optimal foraging theory) at the colony level, and close by providing examples of unexamined questions in this field that are ripe for new inquiries. We conclude that collective personality, as a framework, has the potential to improve our general understanding of how selection acts on intraspecific variation in collective phenotypes that are of key importance across arthropod societies and beyond.