Pollination ecology, specialization, and genetic isolation in sympatric bee pollinated Salvia (Lamiaceae)

Premise of research. Previous pollination ecology studies in Salvia have
shown that there is low specialization to certain subgroups of bees and
that pollinator number varies with species and locality. We studied twelve
Salvia species (three clades with different corolla morphologies and
staminal lever mechanisms) which in part co-occur and co-flower to examine
pre-zygotic isolation mechanisms and the degree of specialization vs.
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 occur among sympatric Salvia species. Morphological
fit is evident between flower tube length and proboscis length of main
pollinators. Pollinator networks indicate that most species are ecological
generalists but only few are specialists. Conclusions. The twelve Salvia
species, though phenotypically and functionally specialized due to their
zygomorphic-bilabiate flowers and bee pollination syndrome, differ in the
degree of ecological specialization. Most of the sympatric Salvia species
tend to be ecologically generalized with two or more main pollinators and
a few additional secondary pollinators, while a few Salvia species are
clearly specialized. Some floral traits (e.g., flower color, morphology,
size, corolla tube length and width of corolla tube entrance, type and
size of the staminal lever mechanism, small numbers of flowers in the
inflorescence), short flowering time, and small population size appear
correlated to the degree of ecological specialization.