Floral syndromes predict the most effective pollinators in five species of Salvia

Pollination syndromes are suites of floral traits associated with the most effective functional group of pollinators. Particular floral traits may not necessarily preclude visitation by different visitor guilds that could also contribute to plant reproduction. The genus Salvia comprises ca. 1000 species with floral traits almost exclusively associated with bee or hummingbird pollination syndromes. Nevertheless, the effectiveness of their floral visitors has rarely been evaluated. Here, the pollination effectiveness of floral visitors in five Salvia species was analyzed to assess the reliability of floral syndromes.

The contribution to seed production of the most frequent floral visitors of Salvia species with melittophilous, ornithophilous, and mixed phenotypes was evaluated through single-visit experiments. In addition, the relationship between floral morphological traits and pollinator effectiveness was explored using principal component analysis to test the reliability of floral syndromes.

Despite multiple floral visitor guilds to the plants, bees and hummingbirds were the most effective pollinators of plants with melittophilous and ornithophilous pollination syndrome, respectively. These two functional groups effectively pollinated the plant species with mixed floral traits. Salvia species pollinated by the same functional group were closer in the multivariate ordination space.

Even when floral syndromes precisely predict the most effective pollinators in Salvia, secondary pollinators also play a crucial role in plant sexual reproduction, especially for plant species with mixed floral phenotypes. This study highlights the importance of evaluating the effectiveness of floral visitors to assess the reliability of floral syndromes.