Pollination Ecology, Specialization, and Genetic Isolation in Sympatric Bee-PollinatedSalvia(Lamiaceae)

Abstract

Premise of research. Previous pollination ecology studies ofSalviahave shown that there is low specialization for certain subgroups of bees and that pollinator number varies with species and locality. We studied 12Salviaspecies (three clades with different corolla morphologies and staminal lever mechanisms) that in part co-occur and coflower to examine prezygotic isolation mechanisms and the degree of specialization versus generalization in pollination ecology. Methodology. Pollinators were identified using field observations, photos, and related literature across three sites in Turkey. Video documentation of the visitation rate and the site of pollen placement on the pollinator body, morphometric measurements between flowers and pollinators, flowering time, flower color, handling time, and stigma contact ratio were analyzed. Plant-pollinator networks were constructed. Pivotal results. Mechanical, phenological, and ethological isolation occurs among sympatricSalviaspecies. A morphological fit is evident between flower tube length and the proboscis length of the main pollinators. Pollinator networks indicate that most species are ecological generalists and that only a few are specialists. Conclusions. The 12Salviaspecies, though phenotypically and functionally specialized by their zygomorphic, bilabiate flowers and bee-pollination syndrome, differ in the degree of their ecological specialization. Most of the sympatricSalviaspecies tend to be ecologically generalized, with two or more main pollinators and a few additional secondary pollinators, while a fewSalviaspecies are clearly specialized. Some floral traits (e.g., flower color, morphology, size, corolla tube length and width of the corolla tube entrance, type and size of the staminal lever mechanism, small numbers of flowers in the inflorescence), a short flowering time, and a small population size appear to be correlated with the degree of ecological specialization.