Avery Russell's Abstracts
Avery Russell
Ph.D. Student
Entomology & Insect Science
Conference Summary
2016 International Congress of Entomology
Orlando, FL
Abstract
Learning of floral preference by bees in the absence of nectar rewards
Avery Russell*, Rebekah Golden*, Anne Leonard**, & Daniel Papaj*
*University of Arizona,**University of Nevada, Reno
Bees foraging on flowers constitute a model system in the study of animal cognition. Although flowering plants offer a variety of rewards and pollinators must collect multiple types of rewards to survive, the literature on bee learning is skewed nearly exclusively towards learning in the context of nectar rewards. Bees in particular must collect two nutritionally complementary floral rewards in order to survive: nectar, their primary source of carbohydrates, and pollen, their primary source of protein. While many flowering plants offer both rewards, 6-8% of angiosperm species offer only pollen rewards. Here we asked if bees can learn preferences for pollen-only species and what components of the flower are involved. To ensure nectar was not involved in learning, we used plant species that offered only pollen as a reward. Using an absolute conditioning protocol, bees were given experience collecting pollen from a single species. Their preference for flowers of that species relative to a second species was tested either one or 24 hours later. We found that the preference of experienced bees was shifted strongly towards the experienced species, relative to the preference of naïve bees. Results of the 24 hour test provided strong evidence of long-term memory. Additionally, we evaluated the role of corolla and anther in learned preferences. While both the corolla and anther responses are involved, anther responses are more strongly influenced by experience. We discuss how learned preferences, such as those shown here, can influence the evolution of floral traits, particularly with respect to pollen-only species.
Abstract for Lay Audience
Learning of Floral Preference by Bees in the Absence of Nectar Rewards
Avery Russell*, Rebekah Golden*, Anne Leonard**, & Daniel Papaj*
*University of Arizona,**University of Nevada, Reno
The floral form is incredibly diverse. Flowers can vary in their color, scent, shape, texture, and size, amongst many other features. Most flowering plant species are visited by animals, which in return for the service of pollination offer rewards, including nectar, pollen, oils, and scents to their pollinators. Because animals may have preferences for particular floral features, pollinators choose to seek out these preferred types and visit them in exclusion to less preferred types. The diversity in floral form is thus thought to be driven by foraging preferences. Pollinator preferences in turn may be learned or innate. Learned preferences involve a learned association between floral traits and the floral reward. As a consequence, such preferences can be formed rapidly and often last for a considerable portion of the pollinator’s lifespan. Because bees in particular can learn many different types of floral stimuli, their learned preferences are considered particularly important to the evolution of floral features. Although flowering plants offer a variety of floral rewards and pollinators must collect multiple types of rewards in order to survive, the literature on bee learning is skewed nearly exclusively towards learning in the context of nectar rewards. Bees in particular must collect two nutritionally complementary floral rewards in order to survive: nectar, their primary source of carbohydrates, and pollen, their primary source of protein, used to feed developing larvae. While many flowering plants offer both rewards, 6-8% of flowering plant species (>20,000 species) offer only pollen rewards.
In this study, we asked (1) if bees can learn preferences for pollen-only species and (2) what components of the flower are involved in the formation of these preferences. To our knowledge, this is the first study to examine innate and learned preferences in a pollen foraging context.
Additionally, even in a nectar foraging context, studies rarely use real flowers, which is surprising because pollinator preferences for live flowers are what directly drive floral evolution. To ensure that nectar was not involved in learning, we used plant species that offered only pollen as a reward. Bees were first given experience collecting pollen from a single species. Their preference for flowers of that species relative to a second species was then tested either one or 24 hours later. We found that the preference of experienced bees was shifted strongly towards the experienced species, relative to the preference of naïve bees. Results of the 24 hour test provided strong evidence of long-term memory. These changes in preference are best explained as associative learning: preference for floral traits formed in association with the paired pollen reward. Additionally, we evaluated the role of petal and anther in learned preferences. While both the petal and anther responses are involved, anther responses are more strongly influenced by experience. This might be expected because the anthers are what produce and hold the pollen reward, while the petals could merely advertise the flower’s presence. We discuss how learned preferences, such as those shown here, can influence the evolution of floral traits, particularly with respect to pollen-only species. We also discuss how these patterns differ from bees foraging for nectar rewards, which mainly learn features of the petals.