Pollinator-dependent evolution of floral trait combinations in an orchid herb

作为驱动花性状进化的重要媒介之一,传粉者塑造了被子植物多样的花部特征。目前,大部分研究集中于传粉者驱动被子植物单个性状的进化,而较少涉及对传粉者驱动被子植物组合性状进化的研究。本研究以兰科植物绶草(Spiranthes sinensis)为材料,分别鉴别和估算了传粉者对植物单个性状和组合性状施加的定向选择和关联选择压力。研究结果表明,传粉者对开花时间和花大小施加定向选择压力,传粉者选择早开花、花更大的个体。传粉者对绶草花展示的组合性状(花大小与花数目)施加正向的关联选择压力,而对开花时间与花展示的组合性状(开花时间与株高、开花时间与花数目)施加负向的关联选择压力。同时,传粉者的选择强度在年际间存在差异。该研究证实了传粉者在驱动植物组合性状进化过程中的作用,同时强调在认识和理解被子植物表型性状进化轨迹时,需要考虑植物组合性状的影响。

Aims As one of the most important agents driving floral evolution,pollinators shape the diversity of flowers in angiosperms.However,most previous studies have only quantified pollinators driving the evolution of a single floral trait,and experimental estimates of the potential role of pollinators in shaping the evolution of floral trait associations are relatively rare.Methods We experimentally identified and estimated the pollinator-mediated directional and correlational selection on single floral traits and trait combinations across 2 years in an orchid species,Spiranthes sinensis.Important Findings Pollinators mediated directional selection for an earlier flowering start date and larger corolla size.Pollinators mediated positive correlational selection on the combinations of floral display traits and negative correlational selection on the combinations of flowering phenology and floral display traits.In addition,the strength of selection differed over time.Our results highlight the potential role of pollinators in driving the evolution of floral trait combinations and suggest that it is necessary to consider floral character functional associations when seeking to understand and predict the evolutionary trajectory of flowers in angiosperms.