Flowers with poricidal anthers and their complex interaction networks—Disentangling legitimate pollinators and illegitimate visitors

Abstract

Abstract In flowers with poricidal anthers, pollen is not freely accessible and legitimate access is restricted to bees capable of vibrating the anthers. Despite the protection of pollen provided by poricidal anthers, numerous illegitimate, non‐buzz‐pollinating flower visitors rob pollen. We aimed to quantify the influence of functional groups of floral visitors and illegitimate interactions on the network structure to disentangle the flower visitor network into its mutualistic and antagonistic components. We delimited three functional groups of bees based on their pollen collection behaviour in poricidal flowers: large bees that vibrate entire flowers in a single buzzing position (flower buzzing), bees vibrating single anthers in different positions (anther buzzing) and non‐vibrating flower‐damaging or gleaning bees (non‐buzzing). Moreover, we characterized legitimate and illegitimate interactions of co‐occurring and co‐flowering plants and their flower visitors based on the stigma contact during a visit. Since we independently assessed the type of interaction with bee–plant species combinations, we were able to include the behavioural variations of each bee species across different flowers. The networks were modular, with stronger interactions within subsets of species than among the subsets. All modules included a combination of flower‐, anther‐ and non‐buzzing bees, and mutualistic and antagonistic networks were intermingled. Seven bee species shifted their roles across plant species. Specialization in the subset of interactions with pollinators was higher than the overall visitation network. Flower‐buzzing bees were more specialized than anther‐buzzing and non‐buzzing bees, which used virtually all poricidal flowers similarly. Although plants with poricidal anthers shared a specialized mechanism of pollen release, their pollinators were highly dissimilar and formed compartments of interacting species. The interaction‐level approach taken in our study confers a high specificity to the pollinator network, leading to a more complex and realistic picture of mutualistic webs versus its embedded florivory, which are otherwise confounded in pooled networks across flower visitors. A plain language summary is available for this article.