Enhancing pollination services LA Garibaldi et al. 440www.frontiersinecology.org

Insect life strategies comprise all levels of sociality from solitary to eusocial, in which individuals form persistent groups and divide labor. With increasing social complexity, the need to communicate a greater diversity of messages arose to coordinate division of labor, group cohesion, and concerted actions. Here we summarize the knowledge on prominent messages in social insects that inform about reproduction, group membership, resource locations, and threats and discuss potential evolutionary trajectories of each message in the context of social complexity.

Like many other bees worldwide, honeybees and bumblebees are threatened by human-induced disturbances. Yet some species decline and others thrive, likely due to different foraging strategies. As little is known about how resource intake translates into nutrients available to colonies, our study aimed to better understand how differences in foraging strategies may affect colony health by relating differences in pollen spectra collected to differences in nutrient composition. The Apis and Bombus colonies studied were all located at the same site, but nevertheless differed in the spectra of plant species visited for pollen collection and the quality of pollen collected. Bumblebees generally collected pollen with significantly higher pollen protein content and more essential amino acids. Unlike honeybees that tend to exploit large resource patches, bumblebees thus seem to select the "better" pollen and to focus on quality instead of quantity.

Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking. We assessed the phenotypic integration of CCDs in a meta-analysis to characterize patterns of covariation in CCDs and identified functional or biosynthetically constrained modules. Poorly integrated plant CCDs (i.e. low covariation between scent compounds) support the notion that plants often utilize one or few key compounds to repel antagonists or to attract pollinators and enemies of herbivores. Animal CCDs (mostly insect pheromones) were usually more integrated than those of plants (i.e. stronger covariation), suggesting that animals communicate via fixed proportions among compounds. Both plant and animal CCDs were composed of modules, which are groups of strongly covarying compounds. Biosynthetic similarity of compounds revealed biosynthetic constraints in the covariation patterns of plant CCDs. We provide a novel perspective on chemical communication and a basis for future investigations on structural properties of CCDs. This will facilitate identifying modules and biosynthetic constraints that may affect the outcome of selection and thus provide a predictive framework for evolutionary trajectories of CCDs in plants and animals.

Preventing malnutrition through consuming nutritionally appropriate resources represents a challenge for foraging animals. This is due to often high variation in the nutritional quality of available resources. Foragers consequently need to evaluate different food sources. However, even the same food source can provide a plethora of nutritional and non-nutritional cues, which could serve for quality assessment. We show that bumblebees, Bombus terrestris, overcome this challenge by relying on lipids as nutritional cue when selecting pollen. The bees 'prioritised' lipid perception in learning experiments and avoided lipid consumption in feeding experiments, which supported survival and reproduction. In contrast, survival and reproduction were severely reduced by increased lipid contents. Our study highlights the importance of fat regulation for pollen foraging bumblebees. It also reveals that nutrient perception, nutrient regulation and reproductive fitness can be linked, which represents an effective strategy enabling quick foraging decisions that prevent malnutrition and maximise fitness.