Shakers and head bangers: differences in sonication behavior between Australian Amegilla murrayensis (blue-banded bees) and North American Bombus impatiens (bumblebees)

Abstract

Many bees collect pollen by grasping the anthers of a flower and vibrating their flight muscles at high frequencies—a behavior termed sonication, or buzz-pollination. Here we compare buzz-pollination on Solanum lycopersicum (cherry tomatoes) by two bees that fill similar niches on different continents—in Australia, Amegilla murrayensis (blue-banded bee), and in North America, Bombus impatiens (bumblebee). We collected audio recordings of buzz-pollination and quantified the frequency and length of buzzes, as well as the total time spent per flower. We found that A. murrayensis buzzes at significantly higher frequencies (~350 Hz) than B. impatiens (~240 Hz) and flaps its wings at higher frequencies during flight. There was no difference in the length of a single buzz, but A. murrayensis spent less time on each flower, as B. impatiens buzzed the flower several times before departing, whereas A. murrayensis typically buzzed the flower only once. High-speed videos of A. murrayensis during buzz-pollination revealed that its physical interaction with the flower differs markedly from the mechanism described for Bombus and other bees previously examined. Rather than grasping the anther cone with its mandibles and shaking, A. murrayensis taps the anther cone with its head at the high buzzing frequencies generated by its flight muscles. This unique behavior, combined with its higher buzzing frequency and reduced flower visit duration, suggests that A. murrayensis may be able to extract pollen more quickly than B. impatiens, and points to the need for further studies directly comparing the pollination effectiveness of these species.