Vegetation context modifies selection on flowering start and plant height in an orchid perennial herb

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.

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

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.