Ecological and evolutionary significance of floral traits – the example of Salvia

Ass. Prof. Dr. Bo Zhang Gansu Agricultural University, Lanzhou, China

Floral diversity has long been considered as the masterpiece of natural selection and the match between flowers and visitors as a testimony for close adaptation. The pollination system in Salvia is the very representative of exquisite interactions between flowers and pollinators. Salvia is characterized by lever-like stamens mediating pollen transfer. Considering the sophisticated interaction with pollinators, it is most likely that this lever system is of susceptibility and instability, and that relevant floral traits might be subject to intense selection in natural populations. Focused on this hypothesis, we first conducted manipulation experiments in S. cyclostegia to test the ecological role of the lever mechanism concerning both the reproductive success of plants and the close interactive relationship with pollinators. We found that the lever mechanism plays a vital role in efficient pollen transferring and contributes to the floral constancy of bumblebees (B. personatus). Furthermore, we investigated into the adaptation of floral traits in two successive years. We found that floral traits of S. digitaloides were subject to intense selection in natural population, and, consequently, that some traits displayed a tendency of divergence under disruptive selection for adaptation to different body-sized pollinators. In conclusion, floral traits involved in the staminal lever mechanism evolved in a functionally integrated manner for the enhancement of pollination efficiency in the population of S. digitaloides.

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