Rewards in a community context

We’re currently (2023) wrapping up an NSF-funded project to explore how the nutritional composition of floral rewards structures interactions between plants, their co-flowering competitors, and bees in Sierra plant communities. This line of research combines lab-based behavioral experiments, chemical ecology of floral rewards, and drone-based techniques to mapping the “nutritional landscape” available to foraging bees. Much of this work was led by PhD student Jacob Francis, and later, Postdoc Anthony Vaudo— they’ve got some cool papers in the pipeline, so stay tuned!

Pollen rewards

Pollen provides bees with many critical macro and micronutrients-- for example, it is their only source of protein. Despite this, remarkably little is known about basic aspects of their pollen foraging behavior. Do our backyard flowers provide bees with high quality protein? How do wild bees respond to huge influxes of protein on the landscape (e.g. through agricultural intensification)? Nutrition plays an important role in bees' response to many kinds of human-driven environmental changes. We're interested in some of the basic questions that may help explain how bees cope with nutritional changes: what kinds of plants offer the most nutritious pollens, and how bees can discriminate between pollen of different species.

We recently provided some of the most direct evidence that bees can assess pollen traits through taste (Biology Letters). Postdoctoral researcher Felicity Muth has also found that bees can learn to associate color patterns with pollen rewards (Animal Behaviour; Biology Letters).

Nectar Chemistry

Nectar is much more than a simple sugar solution. Rather, it is a complex mixture that can contain a brew of secondary compounds at behaviorally relevant doses, amino acids and ions. We are interested in understanding how secondary metabolites affect pollinator biology and behavior, and in exploring how other nectar constituents affect the gustatory preferences and responsiveness of bumblebees (collaboration with Casey Philbin and Chris Jeffrey, UNR Chemistry Dept.). Some of this work on biogenic amines in nectar is out recently (2023) in Muth & Philbin et al. (2022) iScience and Muth et al (2023) Apidologie.

Nutritionally complex floral rewards

Although usually studied separately, many bees collect both nectar and pollen over the course of a foraging bout. EECB PhD student Jacob Francis and Postdoctoral Researcher Felicity Muth are tackling the question of how bees forage for multiple rewards from ecological and cognitive perspectives.

We found that "multitasking" foragers (that collect both pollen and nectar from flowers) can learn that one floral color predicts a nectar reward, whereas another color predicts pollen (Biology Letters). More recently, Felicity found (Behavioral Ecology 2018) that the presence of a pollen fatty acid enhances learning color-nectar associations. In his Behavioral Ecology paper, Jake explores how individual foragers structure their collection of nectar vs. pollen in relation to what the colony needs and what the flower offers.