Experimental disruption of social structure reveals totipotency in the orchid bee, Euglossa dilemma

Abstract

AbstractEusociality has evolved multiple times across the insect phylogeny. Social insects with greater levels of social complexity tend to exhibit specialized castes with low levels of individual phenotypic plasticity. In contrast, species with small, simple social groups may consist of totipotent individuals that can transition among behavioral and reproductive states as the social hierarchy shifts. However, recent work has shown that in some simple social groups, there can still be constraint on individual plasticity, caused by differences in maternal nourishment or initial social interaction. It is not well understood how and when these constraints arise during social evolution, ultimately leading to the evolution of nonreproductive workers. Some species of orchid bees can form social groups of a dominant and 1-2 subordinate helpers where all individuals are reproductive. Females can also disperse on emergence to start their own nest as a solitary foundress, which includes a nonreproductive nest guarding phase not typically expressed by subordinates. Little data exist to characterize the flexibility of orchid bees across these trajectories. Here, using the orchid bee Euglossa dilemma, we conduct an experiment assessing the plasticity of subordinate helpers, finding that they are highly flexible and capable of the behavioral, physiological, transcriptomic, and chemical changes seen in foundresses. Furthermore, we identify genes and gene networks associated with reproductive changes in E. dilemma that overlap with genes associated with worker physiology in eusocial species. Our results provide evidence that the lack of nonreproductive workers in E. dilemma is not due to a lack of subordinate plasticity.