Data from: Selection by pollinators on floral traits in generalized Trollius ranunculoides (Ranunculaceae) along altitudinal gradients

Abundance and visitation of pollinator assemblages tend to decrease with altitude, leading to an increase in pollen limitation. Thus increased competition for pollinators may generate stronger selection on attractive traits of flowers at high elevations and cause floral adaptive evolution. Few studies have related geographically variable selection from pollinators and intraspecific floral differentiation. We investigated the variation of Trollius ranunculoides flowers and its pollinators along an altitudinal gradient on the eastern Qinghai-Tibet Plateau, and measured phenotypic selection by pollinators on floral traits across populations. The results showed significant decline of visitation rate of bees along altitudinal gradients, while flies was unchanged. When fitness is estimated by the visitation rate rather than the seed number per plant, phenotypic selection on the sepal length and width shows a significant correlation between the selection strength and the altitude, with stronger selection at higher altitudes. However, significant decreases in the sepal length and width of T. ranunculoides along the altitudinal gradient did not correspond to stronger selection of pollinators. In contrast to the pollinator visitation, mean annual precipitation negatively affected the sepal length and width, and contributed more to geographical variation in measured floral traits than the visitation rate of pollinators. Therefore, the sepal size may have been influenced by conflicting selection pressures from biotic and abiotic selective agents. This study supports the hypothesis that lower pollinator availability at high altitude can intensify selection on flower attractive traits, but abiotic selection is preventing a response to selection from pollinators.传粉者类群的多度与访花频率往往随海拔升高而降低，进而导致花粉限制（pollen limitation）程度加剧。因此，传粉者资源竞争的加剧可能会对高海拔地区植物的花吸引性状产生更强的选择压，并引发花部的适应性进化。目前鲜有研究将传粉者介导的地理异质性选择与种内花部分化联系起来。本研究以青藏高原东部的毛茛状金莲花（Trollius ranunculoides）为研究对象，探究其花部性状与传粉者类群沿海拔梯度的变化，并量化了不同种群中传粉者对花部性状的表型选择（phenotypic selection）作用。研究结果显示，沿海拔梯度，蜂类的访花频率显著下降，而蝇类的访花频率无显著变化。当以访花频率而非单株结籽数衡量适合度（fitness）时，花萼长宽所受的表型选择强度与海拔呈显著正相关，高海拔地区的选择作用更强。然而，毛茛状金莲花的花萼长宽沿海拔梯度的显著降低，并未与传粉者的更强选择作用相对应。与传粉者访花的影响不同，年平均降水量对花萼长宽呈负向作用，且相较于传粉者访花频率，其对所测定花部性状的地理变异的贡献更大。因此，花萼大小可能同时受到生物与非生物选择因子的冲突性选择压的影响。本研究支持以下假说：高海拔地区传粉者可利用性的降低会强化花吸引性状所受的选择，但非生物选择阻碍了花部性状对传粉者选择的响应。