Abstract
An estimated 20,000 angiosperm species conceal pollen inside tubular
poricidal anthers or within modified petals. A bee releases pollen by
vibrating its thorax and transferring the force through its mandibles
while biting the flower. While the floral morphology of buzz-pollinated
plants is diverse, the behaviors, dimensions and guilds of buzzing bees
are limited. Floral modifications should reflect the relative sizes of
their co-adapted pollinator species but we do not know what drives these
size associations. We show that the optimal excitation point in the
vibration system of bumblebee-pollinated louseworts (Pedicularis)
occurs precisely where bumblebees bite these flowers. This leads to
trait matching between a bumblebee’s individual body length and the beak
length of the flowers of each lousewort species. As bumblebees do not
visit flowers with beaks (galea) longer than their bodies it guarantees
they bite the optimal excitation point for pollen discharge.