Data from: Ecological causes and consequences of flower color polymorphism in a self-pollinating plant (Boechera stricta)

Intraspecific variation in flower color is often attributed to pollinator-mediated selection, yet this mechanism cannot explain flower color polymorphisms in self-pollinating species. Indirect selection mediated via biotic and abiotic stresses could maintain flower color variation in these systems. The selfing forb, Boechera stricta, typically displays white flowers, but some individuals produce purple flowers. We quantified environmental correlates of flower color in natural populations. To disentangle plasticity from genotypic variation, we performed a multiyear field experiment in five gardens. In controlled conditions, we evaluated herbivore preferences and the effects of drought stress and soil pH on flower color expression. In natural populations, purple-flowered individuals experienced lower foliar herbivory than did their white-flowered counterparts. This pattern also held in the common gardens. Additionally, low-elevation environments induced pigmented flowers (plasticity), and the likelihood of floral pigmentation decreased with source elevation of maternal families (genetic cline). Viability selection favored families with pigmented flowers. In the laboratory, herbivores exerted greater damage on tissue derived from white- vs purple-flowered individuals. Furthermore, drought induced pigmentation in white-flowered lineages, and white-flowered plants had a fecundity advantage in the well-watered control. Flower color variation in selfing species is probably maintained by herbivory, drought stress, and other abiotic factors that vary spatially.花颜色的种内变异通常被归因于传粉者介导的选择，但该机制无法解释自花授粉物种的花颜色多态性。生物与非生物胁迫介导的间接选择，或可维持这类系统中的花颜色变异。 自交型草本植物硬叶弯花芥（Boechera stricta）通常开白色花，但部分个体可开出紫色花。我们对自然种群中花颜色与环境因子的相关性开展了量化分析。为区分表型可塑性（plasticity）与基因型变异，我们在5个试验园开展了多年野外试验。在可控条件下，我们评估了植食动物的取食偏好，以及干旱胁迫与土壤pH值对花颜色表达的影响。 在自然种群中，开紫色花的个体相较于开白色花的对应个体，叶片受植食性虫害的程度更轻。该规律在同质园（common garden）试验中同样成立。此外，低海拔环境会诱导植株开出带色素的花（表型可塑性，plasticity）；母本家系的来源海拔越高，其花色素沉着的概率越低（遗传渐变群，genetic cline）。存活力选择更青睐开带色素花的家系。在实验室条件下，植食动物对开白色花个体的组织造成的损伤，显著大于开紫色花的个体。此外，干旱可诱导开白色花的谱系产生色素化花；而在浇水充足的对照组中，开白色花的植株具有繁殖力优势。 自花授粉物种的花颜色变异，可能由植食性虫害、干旱胁迫及其他空间异质性非生物因子共同维持。