Avery Russell Abstract
Avery Russell
Ph.D. Candidate
Entomology & Insect Science GIDP
Society for Integrative and Comparative Biology (SICB) 2015 Annual Meeting
West Palm Beach, Florida
January 3-7, 2015
ABSTRACT
The Role of Experience in Floral Sonication Behavior by a Bumble Bee
Authors: Avery Russell*, Anne Leonard**, & Daniel Papaj*
*University of Arizona,**University of Reno, Nevada
averyrussell@email.arizona.edu(link sends e-mail)
Abstract:
Behavior may vary from being completely pre-programmed, to being readily and extensively modified by experience. When learning has costs, we expect that congenital expression of behavior will be favored. Foraging behavior is one essential activity where the costs of learning could impact the degree of pre-programming. While the majority of angiosperms offer two nutritionally complementary rewards to bees, pollen and nectar, most studies have focused on nectar foraging. Floral morphologies vary considerably and complex designs that offer nectar can require extensive learning. Little is known about costs of pollen foraging however, even though it is the sole protein source for larval and adult growth, and thus essential for survival. Six-8% of angiosperms offer only pollen, concealed in specialized poricidal anthers. Only bees that are able to vibrate the anthers and thus shake the pollen out (a complex behavior termed floral sonication) can access this essential nutrient. While we know a great deal about the function of sonication, the degree to which learning plays a role in shaping this behavior is an open question. In the Eastern Bumble Bee (Bombus impatiens) we find that the sonication motor routine is strongly congenitally expressed. Sonication behavior is rapidly released upon discovery of the androecium and is mediated by chemical cues from the anthers. We show evidence that a decrease in latency to sonicate with experience is likely a result of priming or imprinting, involving a heightening of responses to releaser stimuli. While anther cues appear to release sonication innately, petal cues release landing behavior innately. However, with experience, anther cues also promote landing.
Abstract (for Lay Audience):
Behavior may vary from being completely pre-programmed, to being readily and extensively modified by experience. When learning is costly, we expect that congenital expression of behavior will be favored. Foraging behavior is one essential activity where the costs of learning could impact the degree of pre-programming. While most angiosperms (flowering plants) offer two nutritionally complementary rewards to bees, pollen (the plant’s male gametes) and nectar, the vast majority of studies have focused on nectar foraging. Floral morphologies vary considerably and bees require extensive experience to efficiently access the concealed nectar rewards of complex flowers. Almost nothing is known about the costs of pollen foraging however, even though it is the sole protein source for larval and adult growth. Pollen collection is therefore an essential foraging activity for both bee and plant reproductive success. Six-8% of angiosperms offer only pollen as a floral reward, concealed in specialized poricidal anthers. Only bees that are able to vibrate the anthers and thus shake the pollen out (a complex and energetically costly behavior termed floral sonication) can access this essential nutrient. While we know a great deal about the function of sonication, the degree to which learning plays a role in shaping this behavior is unknown. Does detecting and retrieving concealed pollen rewards require a substantial amount of experience, as it does with concealed nectar rewards?
In the Eastern Bumble Bee (Bombus impatiens), a pollinator that visits many species of angiosperms, we find that the sonication motor routine is strongly congenitally expressed. Flower-naïve bees do not require practice to perform the correct order of steps in the sonication motor routine. Likewise the motor routine is heavily stereotyped. Furthermore, sonication behavior is rapidly released upon discovery of the anthers and is mediated by chemical cues from these organs. After first finding the anthers (or an anther extract presented on artificial flowers), flower-naïve bees take several seconds to initiate floral sonication. However, after the first visit, the latency to sonicate drops significantly and stays low for subsequent visits in the same day. This decrease in latency to sonicate with experience is likely a result of priming or imprinting, involving a heightening of responses to releaser stimuli. While anther cues appear to release sonication innately, petal cues release landing behavior innately. However, with experience, anther cues also promote landing.
With this data we present evidence that buzz pollination represents a much tighter coevolution than previously thought. Not only may other bee species not need to learn how to sonicate, but sonication on many different poricidal flowers is innately released. Despite the independent evolution of buzz pollination behavior and poricidal flowers in a number of taxa, the chemical cues and behavioral routines in this mutualism could be expected to show extensive convergence in their evolution. On the other hand, experience does play an important role in shaping how bees detect and assess flowers. Since poricidal morphologies vary considerably across species, even though floral sonication is released innately, learning still should improve efficiency of pollen foraging.