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| Bumblebee (left) and ant (right) in blueberry flowers |
By Castro et al.
Highbush blueberry, a pollinator-dependent crop, attracts a wide range of insects, including managed honeybees, wild bees, and hoverflies. But not every visitor is equally effective. Blueberry flowers can be challenging for pollinators: their shape limits access to nectar and pollen, while their poricidal anthers release pollen more efficiently when vibrated, a process known as buzz pollination. Visitors also differ in how they forage and how much pollen they carry and deposit.
We monitored visitors to the highbush blueberry cultivar ‘Duke’ and found a surprise: most visits came from the ant Formica rufibarbis, followed closely by the bumblebee Bombus terrestris. To compare their effectiveness, we allowed individual insects to visit previously bagged flowers, then measured the pollen they deposited. Only Formica rufibarbis and Bombus terrestris visited flowers during this experiment.
Bumblebees deposited significantly more pollen tetrads than ants, and the flowers they visited developed more pollen tubes. Even so, unbagged flowers exposed to open pollination developed more pollen tubes than flowers visited just once by a bumblebee. This suggests that repeat visits by bumblebees, contributions from other pollinators, or both may increase pollen deposition.
Ants were less effective blueberry pollinators because they deposit less pollen and may promote self-fertilization. Yet when flying pollinators are scarce, for example, during unfavorable weather or early in the flowering season, large numbers of ants could still make a valuable contribution to the pollination of this crop.
