Stone J D, Olson M S
Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA.
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.
J Evol Biol. 2018 Jan;31(1):111-122. doi: 10.1111/jeb.13203. Epub 2017 Nov 21.
Gynodioecy, the co-occurrence of females and hermaphrodites, is arguably the most common angiosperm gender polymorphism in many florae. Females' ability to invade and persist among hermaphrodites depends, in part, on pollinators providing adequate pollination to females. We directly measured diurnal and nocturnal pollinators' contributions to female and hermaphrodite seed production in artificial populations of gynodioecious Silene vulgaris by experimentally restricting pollinator access. We found that female relative seed production in this system depended strongly on pollination context: females produced more than twice as many seeds as hermaphrodites in the context of abundant, nectar-collecting moths. Conversely, females showed no seed production advantage in the context of pollen-collecting syrphid flies and bees due to acutely hermaphrodite-biased visitation. We infer that variation in pollinator type, behaviour and abundance may be important for achieving the female relative fitness thresholds necessary for the maintenance of gynodioecy. Generally, our study illustrates how pollinator-mediated mechanisms may influence the evolution of breeding systems and associated suites of floral traits. Segments of a pollinator community may facilitate gynodioecy by selecting for plant characteristics that increase the attractiveness of both sexes to pollinators, such as nectar rewards. Conversely, discriminating visitors in search of pollen may restrict gynodioecy in associated plant lineages by reducing male steriles' fitness below threshold levels.
雌全异株现象，即雌性植株和雌雄同体植株共存的现象，可以说是许多植物区系中最常见的被子植物性别多态性。雌性植株在雌雄同体植株中入侵并持续存在的能力，部分取决于传粉者为雌性植株提供充足的授粉。我们通过实验限制传粉者的访问，直接测量了昼夜传粉者对雌全异株植物普通麦瓶草人工种群中雌性和雌雄同体植株种子产量的贡献。我们发现，在这个系统中，雌性植株的相对种子产量在很大程度上取决于授粉环境：在有大量采集花蜜的蛾子的环境中，雌性植株产生的种子数量是雌雄同体植株的两倍多。相反，由于传粉者明显偏向于访问雌雄同体植株，在采集花粉的食蚜蝇和蜜蜂的环境中，雌性植株没有种子产量优势。我们推断，传粉者类型、行为和数量的变化可能对达到维持雌全异株现象所需的雌性相对适合度阈值很重要。一般来说，我们的研究说明了传粉者介导的机制可能如何影响繁殖系统以及相关花部性状组合的进化。传粉者群落的某些部分可能通过选择能增加两性对传粉者吸引力的植物特征（如花蜜回报）来促进雌全异株现象。相反，寻找花粉的有偏好的访花者可能会通过将雄性不育植株的适合度降低到阈值水平以下，来限制相关植物谱系中的雌全异株现象。
