The role of intraspecific variation in bumblebee body size and behavior on buzz pollination of a tropical legume species

Abstract

PremiseThe outcomes of generalized mutualisms rely on partner trait variation. In pollination mutualisms, although less explored, intraspecific variation in pollinator traits can be pivotal for successful pollination. We investigated the role of intraspecific body size and behavioral trait variations of bumblebee Bombus morio on the pollination of a buzz‐pollinated legume species, Chamaecrista latistipula.MethodsTo explore the impact of body size and behavior of B. morio on the pollination of C. latistipula, we observed visits to virgin flowers and quantified the pollen removal and deposition (pollination performance) and fruit and seed production (reproductive fitness). By analyzing video and sound recordings, we measured B. morio body size and behavior on each flower, including bee vibration descriptors.ResultsWe observed intraspecific behavioral differences among B. morio bumblebees associated with different body sizes. Larger bumblebees had half the handling time and vibrational pulses, less angular displacement within flowers, and larger relative peak amplitudes during vibrations than smaller bumblebees did. Regardless of their large variation in size and behavior, bumblebees were equally effective in removing pollen and pollinating flowers. The high female reproductive fitness was independent of bumblebee body size and behavior, likely due to the interaction between both. On the other hand, larger bumblebees visited flowers for shorter periods, probably promoting higher male reproductive fitness.ConclusionsThis study is the first to highlight the large intraspecific variation of bumblebee body size and behavior in buzz‐pollinated flowers in the field. Together, body size and behavior effects unexpectedly cancel each other, generating a high buzz pollination efficiency.

Biomechanical properties of defence vibrations produced by bees

“…Our results suggest that, all else being equal, a larger bee should be able to remove more pollen per time spent buzzing than a smaller bee. This does not mean that smaller bees are at a disadvantage in terms of total pollen removal, as the behaviour of the bee on the flower will affect how these vibrations are applied to the flower and the amount of pollen removed, and small bees might adjust how they manipulate and interact with flowers to maximise pollen removal (Barbosa et al, 2023; Delgado et al, 2023).…”

“…Bee size might also affect other properties of bee vibrations such as buzz duration. Empirical measurements of the duration of pollination buzzes in bumblebees suggests that larger individuals produce shorter buzzes (Barbosa et al, 2023; De Luca et al, 2014). However, this does not necessarily imply that larger bees are incapable of producing longer buzzes, and instead could simply reflect that a larger bee can extract more pollen with a short buzz than a smaller bee.…”