Abstract:

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.

Key words: fitness, phenotypic selection, pollinator preference, flowering time, floral trait, Trollius ranunculoides