Pollenkitt is associated with the collectability of Malvoideae pollen for corbiculate bees

by Sabine Konzmann, Mona Neukirchen, Dagmar Voigt, Christoph Neinhuis & Klaus Lunau

Bumble bee collecting pink pollen of
Malope trifida on its hind legs (above);
bumble bee densely covered with pale
yellow pollen of Hibiscus syriacus,
but unable to collect it (below)

Bees transfer pollen grains between flowers, but they also collect and thus withhold pollen which is no longer available for pollination. Flowers of the Malvaceae family typically possess large and spiny pollen grains that cannot be collected by corbiculate bees such as honey bees and bumble bees. However, there are a few exceptions that prove pollen size and spines do not intrinsically prevent pollen collection by corbiculate bees. More specifically, the stickiness of the pollenkitt as measured in centrifuge experiments might play a crucial role in determining the collectability of Malvaceae pollen grains. Washing pollen with hexane removes all pollenkitt, whereas washing pollen with water removes pollenkitt on the collectable pollen grains of Malope trifida, but not on the uncollectable pollen grains of Hibiscus syriacus. Pollenkitt consistency might elicit excessive viscidity which improves adhesion to insect visitors, but prevents pollen collection by corbiculate bees. As a consequence, these flowers are only visited by nectar-foraging corbiculate bees - which facilitates the reproduction of the plants.

Read the scientific publication in JPE