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（pollinator assemblages）的丰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）加剧。由此，传粉者资源竞争的加剧可能对高海拔地区植物的花部吸引性状产生更强的选择压力，并推动花部适应性演化。目前鲜有研究将传粉介导的地理变异选择与种内花部分化关联起来。
我们针对青藏高原东部（eastern Qinghai-Tibet Plateau）的毛茛状金莲花（Trollius ranunculoides）沿海拔梯度的花部性状及其传粉者类群展开了调查，并量化了不同种群中传粉者对花部性状的表型选择（phenotypic selection）强度。结果显示，蜂类的访花率随海拔梯度显著下降，而蝇类的访花率无明显变化。当以访花率而非单株种子数衡量适合度（fitness）时，花萼长与花萼宽所受的表型选择强度与海拔呈显著正相关，即高海拔地区的选择压力更强。
然而，毛茛状金莲花的花萼长宽随海拔升高呈现的显著下降趋势，并未与传粉者施加的更强选择相匹配。与传粉者访花率的影响不同，年平均降水量（mean annual precipitation）对花萼长宽呈现负向影响，且相较于传粉者访花率，其对所观测的花部性状地理变异的贡献更大。
因此，花萼大小可能同时受到生物选择因子（biotic selective agents）与非生物选择因子（abiotic selective agents）的冲突性选择压力调控。本研究支持如下假说：高海拔地区传粉者可利用性的降低会强化对花部吸引性状的选择，但非生物选择压力阻碍了花部性状对传粉者选择的响应。