Floral evolution: breeding systems, pollinators, and beyond

Buzz pollination is a phenomenon whereby flowers require vibration by insects to release pollen through pores at the anther tips. It occurs in over 20,000 plant species, including some economically important crops. Buzz-pollinated plants have complex floral morphologies, in which enlarged anthers serve as the main organ for interacting with buzzing pollinators (usually bees). Despite a long-standing interest in buzz pollination, we know relatively little about how anther morphology affects the release of pollen by buzz pollinators. Here, we analyse the ultrastructure of buzz-pollinated flowers using high-resolution X-ray micro-computed tomography (micro-CT) of six Solanum (Solanaceae) taxa. These taxa have flowers that vary markedly in anther morphology and overall size. Using measurements obtained from micro-CT scans, we compared anther morphology in closely related species with different reproductive strategies, and documented how pollen is stored inside the anthers. We speculate on how anther morphology, including anther traits, may modulate the response of flowers to the vibrations produced by bees during buzz pollination.