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厘清背景环境因素(本研究定义为目标植株周围物种的数量、密度以及植株高度)对植物花性状获得表型选择压力的影响,是认识和预测同域开花物种-种间竞争环境下植物花性状进化模式和进化轨迹的关键环节;同时,对认识和理解传粉者施加的表型选择在时空上的变化具有重要作用.本研究以兰科多年生草本植物绶草(Spiranthes sinensis)为材料,通过人为降低绶草周围植株高度,连续两年定量衡量背景环境因素分别通过结实数和花粉输出途径对绶草4个花性状(开花时间、株高、花冠大小和花数目)获得表型选择的影响.研究结果表明,降低周围植株高度导致的背景环境改变对开花时间和株高等表型性状具有选择作用:改变了的背景环境选择开花时间更早、株高更矮的绶草植株个体,且两类性状获得的表型选择强度于年际间存在差异.进一步研究表明,这种背景环境的改变通过雌性适合度产生的影响强于通过雄性适合度.本研究证实了背景环境因素在驱动被子植物花性状分化和塑造花多样性过程中的潜在作用.“,”Aims Identifying the potential role of vegetation context(defined as the density,species identity/diversity and height of co-occurring plants)in modifying selection on floral traits is a critical step for clarifying and predicting the floral evolutionary trajectory in complex co-flowering species competition environments.It is also helpful to understand the variation in pollinator-mediated selection.Methods We experimentally reduced vegetation height around individual plants of Spiranthes sinensis(a bumblebee-pollinated perennial orchid herb)and estimated how vegetation context modified selection on four floral traits(flowering start,plant height,corolla size and number of flowers)through female function and pollen removal over two continuous years.We randomly selected independent plants in each year.Important Findings We demonstrated that vegetation context modified selection for earlier flowering start and shorter plant height of S.sinensis.The strength of selection differed between years.In addition,selection was stronger through female function than through pollen removal.Our findings indicate the potential role of vegetation context in shaping the differentiation and diversification of flowers in angiosperms.