为了研究植物生长季内开花时间对花特征表型选择的影响, 我们以青藏高原东缘高寒草地的毛茛状金莲花(Trollius ranunculoides)为实验材料, 在生长季内不同开花时间(花前期、花末期)测定花特征, 观察访花昆虫的类群和访花频率, 生长季结束后收集种子。根据昆虫访花的喜好和季节内类群与访花频率的变化, 分析了不同开花时间毛茛状金莲花的花特征与昆虫的选择; 并用种子产量表示雌性适合度, 估计了毛茛状金莲花的花特征在不同开花时间所受的表型选择。结果表明: 不同花期植物的花特征有显著差异, 相应的访花昆虫的类群和频率也存在差异, 不同类群昆虫访花喜好也不一样。蜂喜好花瓣和花萼较宽、花茎短和花茎数少的个体, 这正符合花前期的特征, 因而蜂的访花频率在花前期较高; 蝇对花特征没有明显的偏好。而通过雌性适合度估计毛茛状金莲花花特征所受的表型选择则是: 花前期, 花茎较长和花茎数多的植株适合度大; 花末期, 花茎数多的植株适合度大。我们的研究表明: 在植物生长季, 花期的分化伴随着传粉昆虫活动的变化。不同花期, 访花昆虫的变化可能对植物花特征的分化起了至关重要的作用。但是访花昆虫对花特征的选择与通过雌性适合度估计植物受到的选择不尽相同, 这可能是由于其他因素造成的。

We measured floral traits of Trollius ranunculoides at different flowering time, observed the taxa of pollinators and pollinator visiting frequencies, and collected the seeds in the end of growing season to estimate pollinator preferences and the overall phenotypic selection gradient. We estimated phenotypic selection on floral traits at different flowering time using female fitness (seed number). We found significant differences of floral traits among different flowering time, with the corresponding preference, taxa, and visiting frequencies of pollinators also different. During early flowering time, visiting frequencies of bees were higher, flower calxy and petal size were wider, and total stalk length was shorter on flowers that bees preferred; however, there was no significant flower preference by different fly species. Furthermore, our estimates of phenotypic selection through female fitness differed at variable flowering time. The results of our study indicate that divergent flowering time and corresponding variation in pollinators might lead to different phenotypes, ultimately resulting in the divergence of floral traits. However, pollinator preference was dissimilar from phenotypic selection estimated by female fitness due to reasons not sufficiently evaluated in this study.