Species-specific perceptional hierarchies underlying the detection of nutritional and non-nutritional compounds in pollen collected by bees

• Applicants: Professorin Dr. Sara Diana Leonhardt; Privatdozent Dr. Johannes Spaethe
• Subject Area: Sensory and Behavioural Biology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 313898935

Bees decline worldwide and both scientists and public worry about the observed trends and wonder about the underlying mechanisms. Many of the discussed culprits are directly or indirectly linked to food resource availability and quality and thus nutrition. We hardly know, however, how variation in nutritional quality affect bee foraging choices and subsequently fitness. In our previous project, we showed that nutrient perception, nutrient regulation and fitness are linked for pollen collection in bumblebees, i.e. that bumblebees prioritize perception of and regulate fat which has also the strongest fitness consequence. Such ‘prioritized perception’ of nutritional cues, closely linked to fitness, may represent a valuable, highly efficient and evolutionary beneficial strategy for foraging bees. We further revealed that the contents of different nutrient groups (e.g. amino acids and fatty acids) in pollen are correlated. We consider such ‘nutritional correlates’ a prerequisite for prioritized compound perception and hypothesize that ‘compound correlates’ also occur between nutritional compounds, floral scent compounds and potentially even color as a consequence of shared biosynthetic pathways.In our renewal proposal, we aim to (i) unravel the factors that determine perceptional hierarchies of compounds (such as compound toxicity, concentrations, foraging strategies and/or degree of sociality) in different bee species, (ii) investigate ‘compound correlates’ beyond nutrients, and (iii) expand into the field to test if our findings under controlled laboratory conditions can explain flower visitation patterns of bees in a natural floral community. Preliminary studies suggests that prioritized perception and regulation differs between bee species. We will therefore compare perceptional hierarchies of compounds in pollen quality assessment and their fitness consequences between four bee species, which differ in the degree of sociality and food specialization. We will also test whether nutritional cues perceived by bees correlate with non-nutritional cues (i.e. scent, color), which could enable bees to associate nutritional quality with non-nutritional cues and therefore to infer information on the nutritional appropriateness of pollen already from a distance. By expending our work to the field and collecting data on pollen foraging behavior, pollen chemistry and floral color and scent from natural communities, we will finally determine how well our conclusions on compound perception (drawn from few species) predict pollen foraging choices under natural conditions.We believe that our project will not only enable a better understanding of the relationship between the nutritional quality of resources, chemical perception and animal foraging behavior and strategies, but also provide important knowledge for supporting bee conservation and pollination stability.

• DFG Programme: Research Grants