Reproductive Biology and Delayed Selfing in Viola pubescens (Violaceae), an Understory Herb with Chasmogamous and Cleistogamous Flowers

Abstract

Plant response to variation in the surrounding biotic and abiotic environment often involves mechanisms that promote reproductive assurance. The goal of this study was to determine whether production of chasmogamous (CH) and cleistogamous (CL) flowers as well as delayed CH selfing in the perennial herb Viola pubescens enhances reproductive output in a heterogeneous environment. A central Ohio population was monitored for several years to study its reproductive biology and to measure selfing rates in CH flowers. A temporal switch from CH to CL flowers corresponded with a reduction in light availability as the forest canopy formed. Although similar numbers of CH and CL flowers were produced per plant, CH flowers were nearly twice as likely to disperse seeds as CL flowers. Both floral types had similar numbers of seeds with comparable mass, and there was no difference in emergence of CH and CL seedlings. In addition to outcrossing, CH flowers were capable of delayed selfing if left unvisited by insect pollinators. This was consistent with the rate of selfing over a 2‐yr period (0.60, 0.07) measured with allozymes. Both CH and CL flowers contributed to reproduction in V. pubescens as well as delayed CH selfing, thereby creating a mating system that may be an adaptation to pollinator or resource unpredictability within the flowering season.