Asymmetric effects of loss and gain of a floral trait on pollinator preference

Shifts in pollination syndromes involve coordinated changes in multiple floral traits. This raises the question of how plants can cope with rapid changes in pollinator availability by the slow process of accumulation of mutations in multiple genes. Here we study the transition from bee to hawkmoth pollination in the genus Petunia. Interspecific crosses followed by single locus introgressions were used to recreate putative intermediate evolutionary stages in the evolution of moth pollination. The effect of the loss/gain of petal color was asymmetric: it had no influence on the established pollinator but enhanced visitation by the new pollinator. Therefore, shifts in pollination syndromes may proceed through intermediate stages of reduced specialization and consequently enhanced reproductive assurance. The loss of petal color in moth-pollinated Petunia involves null mutations in a single regulatory gene, An2. Such simple genetic changes may be sufficiently rapid and frequent to ensure sur...传粉综合征（pollination syndromes）的演化转变涉及多个花部性状的协同改变。这一现象引出了一项关键科学问题：植物如何通过多个基因中突变累积的缓慢过程，应对传粉者可利用性的快速变化？本研究以矮牵牛属（Petunia）为研究材料，探究其从蜂类传粉向天蛾传粉的演化转变。研究通过种间杂交结合单基因渐渗技术，成功重现了天蛾传粉演化历程中推测的中间演化阶段。花瓣颜色的丢失或获得具有不对称效应：其对已建立适配关系的传粉者无显著影响，但可提升新传粉者的访花频率。由此可知，传粉综合征的转变可通过特化程度降低的中间阶段推进，进而提升生殖保障能力。天蛾传粉的矮牵牛类群中，花瓣颜色的丢失源于单个调控基因An2的无效突变。这类简单的遗传改变或许足够快速且频繁，足以确保sur...