Selfing strategy in the mixed mating system of Tulipa sinkiangensis in unstable pollination environment in early spring

Abstract

Abstract [Objective] In unstable pollination environments, bisexual flowering plants often possess potential selfing ability. Given the mating cost of selfing, investigating selfing strategies in different environments are critical for the understanding of evolution of the mating systems. [Methods] To explore the selfing strategies of plants in the unstable pollination environments in early spring, we studied the flowering habits, pollinator groups, pollen dispersal dynamics, self-pollen transfer patterns, and mating systems in a natural population of Tulipa sinkiangensis, an early spring ephemeral plant. [Results] (1) T . sinkiangensis bloomed in early or mid April, with a single flowering period of 5-6 days. Flowers opened during the day and closed at night. Pollen dispersal started from the outer and appeared in a zippered order from bottom to top. (2) The pollinators were mainly bees and syrphids. Visiting frequencies were low, with great fluctuation among years, but the fruiting rates were generally higher in natural populations. (3) In the unstable pollination environment in early spring, the population was mainly outbred and partly self-inbred, forming a mixed mating system. The autonomous stamens movement during the closing of flowers in the evening promoted the autonomous self-pollination, and the massive deposition of self-pollen occurred on the 4th day after flowering, accounting for 50.22% of the total autonomous self-pollen deposition. It was a delayed self-pollination pattern, although promoting the occurrence of competing selfing. [Conclusion] Under limited pollination, the competing and delayed selfing promotes pollen deposition in T . sinkiangensis. This mating strategy that combined outcrossing, competing selfing, and delayed selfing flexibly responds to the unstable pollination environment in the early spring. It is an adaptation to the unstable pollination services under the low temperature condition in the early spring, and also a reproductive assurance strategy for the early spring ephemeral plants.

Keywords

• tulipa sinkiangensis
• spring ephemeral plant
• stamen movement
• delayed selfing
• competing selfing