Data from: Loss of color pigmentation is maintained at high frequency in a monkey flower population

Color polymorphisms have long been of evolutionary interest for their diverse roles, including mate choice, predator avoidance, and pollinator attraction. While color variation is often under strong selection, some taxa demonstrate unexpectedly high frequencies of presumed deleterious color forms. Here we show that a genetic variant underlying complete loss of anthocyanin pigmentation has risen to an unexpectedly high frequency of >0.2 in a natural population of the plant Mimulus guttatus. Decreased expression of MYB5 transcription factor is associated with unpigmented morphs. While the allele was found only in heterozygote adults in the wild, suggesting negative selection, experiments were unable to demonstrate a fitness cost for unpigmented plants, suggesting a cryptic selection pressure in the wild. However, life-history differences among morphs suggests that unpigmented individuals benefit from later flowering and clonal growth. Overall, our study highlights the complex interplay of factors maintaining variation in nature, even for genes of major effect.

花色多态性（color polymorphisms）长期以来备受进化生物学领域关注，因其在配偶选择、天敌规避、传粉者吸引等多个环节中发挥多样功能。尽管花色变异通常受到强烈选择压的作用，但部分类群却呈现出异常高频率的、被认为具有有害性的花色表型。本研究表明，导致完全丧失花青素（anthocyanin）沉着的遗传变异，在植物沟酸浆（Mimulus guttatus）的自然种群中已达到>0.2的异常高频频率。MYB5转录因子（MYB5 transcription factor）的表达下调与无色素表型密切相关。尽管该等位基因（allele）在野外仅以杂合子成年个体的形式被检测到，提示存在负选择，但实验并未证实无色素植株存在适合度代价，这暗示野外存在隐秘的选择压力。不过，不同表型间的生活史差异表明，无色素个体可通过较晚开花与克隆生长获得生存优势。综上，本研究揭示了自然界中维持遗传变异的多种因素间的复杂相互作用，即便对于具有主效效应的基因亦是如此。