Effective hawkmoth pollination in the primarily bee‐pollinated Salvia daiguii—an example of adaptive generalization

Abstract

AbstractMany plants exhibit floral traits that are directed to specific pollinator groups. Nevertheless, they can also attract less‐adapted pollinators and gain benefits under certain conditions, resulting in adapted generalization. This may be the case in Salvia daiguii (Lamiaceae), an endangered, bee‐pollinated species native to the Tianmenshan National Forest Park, China. The flower appears phenotypically specialized to bees but is also visited by Macroglossum bombylans. In the present study, we test whether the moth is an effective pollinator of S. daiguii. We quantified and compared the frequency of flower visits by bees and moths and the number of pollen grains deposited on the stigma after a single visit. We also recorded the movements of pistils and stamens of S. daiguii and the behavior of the hawkmoth at the flowers. We found that Apis cerana was the predominant pollinator, depositing an average of 4.74 pollen grains on the stigma after a single visit. However, as the style bends downward during anthesis and reaches the same level as the anthers, Macroglossum individuals hovering around the flowers were also able to effectively transfer pollen to the stigma. On average, 1.38 pollen grains were deposited on the stigma during a single visit. We demonstrate for the first time that the hawkmoth is an effective secondary pollinator in the primarily bee‐pollinated S. daiguii. Style bending allows a nectar thief to become a secondary pollinator. The extent of pollinator generalization is thus increased without affecting the fundamental phenotype adapted to bees as the main pollinators.