Multiple aggressions among nestmates lead to weak dominance hampering primitively eusocial behaviour in an orchid bee

Abstract

Reproductive conflict expressed as aggression is common in social Hymenoptera. In eusocial species, as in honeybees, several mechanisms however alleviate the conflicts and reduce aggressive interactions. Unlike their sister group, the orchid bees do not exhibit eusocial behaviour. Instead, some of the species presents a primitively eusocial behaviour, with a single dominant female and fertile subordinate females participating on egg laying activities. In the current study we investigated the aggressive interactions of Euglossa annectans Dressler females through five generations of phylopatry and reuse of the natal nest. Although network analysis indicates that central individuals, those with more interactions, were more commonly the aggressors and others were more commonly the recipients, multiple attacks and several potential dominant females within the nest indicated a labile sociality. This suggests that there is an unstable social hierarchy in the species. Euglossa annectans, despite having overlapping generations, during which several individuals share a nest, there is no division of labour into reproductive females and interactions are often competitive. Aggressive behaviours conducted by multiple fertile females were often followed by egg, larvae or pupae replacement.