Natural selection acts on phenotypic trait variation. Understanding the mechanisms that create and maintain trait variation is fundamental to understanding the breadth of diversity seen on Earth. Flower colour is among the most conspicuous and highly diverse traits in nature. Most flowering plant populations have uniform floral colours, but a minority exhibit within-population colour variation, either discrete (polymorphic) or continuous. Colour variation is commonly maintained by balancing selection through multiple pollinators, opposing selection regimes, or fluctuating selection. Variation can also be maintained by heterozygote advantage or frequency-dependent selection. Neutral processes, or a lack of selection, may maintain variation, although this remains largely untested. We suggest several prospective research directions that may provide insight into the evolutionary drivers of trait variation.

自然选择作用于表型性状变异。了解造成和维持性状变异的机制是理解地球上多样性的基础。花的颜色是自然界中最显着和高度多样化的特征之一。大多数开花植物种群具有统一的花色，但少数群体的种群内颜色变化不连续（多态）或连续。通常通过通过多个授粉媒介平衡选择，相反的选择方式或波动的选择来维持颜色变化。也可以通过杂合子优势或频率依赖性选择来维持变异。中性过程或缺乏选择可能会保持变异，尽管这在很大程度上未经测试。