Saleh, N. W. | bioRxiv Science

bioRxiv2022

The function of environmentally acquired perfume blends in male orchid bees

Perfume making by male orchid bees is a remarkable behavior giving rise to an entire pollination syndrome in the neotropics. Male orchid bees concoct and store perfume mixtures in specialized hind-leg pockets using volatiles acquired from multiple environmental sources, including orchids. However, the precise function and ultimate causes of this behavior have remained elusive. We supplemented male Euglossa dilemma reared from trap-nests with perfume loads harvested from wild conspecifics. In dual-choice experiments, males supplemented with perfumes mated with more females, and sired more offspring, than untreated, equal-aged, control males. Our results demonstrate that male-acquired perfumes function as chemical signals emitted during courtship and received by females when selecting mates. Sexual selection might be a key agent shaping the evolution of perfume signaling. One-Sentence SummaryThe possession of exogenous volatiles increase male mating success and paternity in orchid bees.

evolutionary biology↗

bioRxiv2022

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

Eusociality 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.

evolutionary biology↗