Is the occluded corolla of Antirrhinum bee-specialized?

Abstract

This paper provides the first results of pollinator fauna associated to the reproductive biology of Antirrhinum charidemi, Antirrhinum graniticum and Antirrhinum braun-blanquetii. Censuses of over 16 hours spanning the flowering phenology of each species were drawn up. As previously hypothesized, the characteristic occluded (personate) corolla of Antirrhinum was exclusively pollinated by bees, but by a higher number (four) of bee families than predicted. Seven bee species (Bombus hortorum, Anthidium manicatum, Chalicodoma lefebvrei, Anthidium sticticum, Anthophora dispar, Xylocopa violacea and Anthidium cingulatum) account for over 90% of flower visits (2098). The flower visitation index varied between species (0.0126−0.0320), reaching relatively medium values compared to Mediterranean plants. In contrast, reproductive success was found to be high when estimated as both fruit (45.4–84.2%) and seed (75.4–98.4%) sets, suggesting that these bee guilds are effective pollinators of the three self-incompatible Antirrhinum species. Specialization of the personate flower of Antirrhinum is therefore interpreted for bees with both large bodies and high visitation indices.

Keywords:

• Antirrhinum braun-blanquetii
• Antirrhinum charidemi
• Antirrhinum graniticum
• bee species; mediterranean
• reproductive success

Acknowledgements

We thank Cormac de Brun for editing the English of this paper, Javier Sánchez for help in the field, Rocío Santos for reference searches and the Natural Park of Níjar and cabo the Gata for help in conservation of Antirrhinum charideni.