Aims Competition for pollinators between phenotypically similar flowers is believed to play an important role in floral trait diversification in the angiosperms.However,in many plant communities,species with apparentl...Aims Competition for pollinators between phenotypically similar flowers is believed to play an important role in floral trait diversification in the angiosperms.However,in many plant communities,species with apparently similar floral phenotypes and generalist pollina-tion systems co-flower.Here,the pollination systems of Ranunculus acris L.and Ranunculus repens L.were investigated to determine the factors enabling the species to coexist within apparently over-lapping pollination niches.Methods Sympatrically flowering populations of R.acris and R.repens were investigated at three study sites in West Wales.The flo-ral phenotypes of the two species were compared using meas-urements of floral morphology and spectral analyses of petal reflectance,using principal component analysis and bee and fly colour-space models.Evidence of inter-specific discrimina-tion by foraging insects was tested for in the field and using floral arrays.The relative roles of behavioural constancy and spatial patchiness in maintaining pollinator fidelity were estimated.Important Findings The floral phenotypes of R.acris and R.repens differed significantly.Social bees were highly constant when foraging at flowers of the two species and patchy floral distribution explained some of the observed fidelity.Dipterans visiting mixed floral arrays appeared to discriminate between the species,visiting more R.acris than R.repens flowers,but there was no difference in the number of vis-its to single-species arrays.Social bees were more likely to display constancy to flowers of R.repens in the field.Patchiness in floral distribution,subtle differences in floral phenotype,pollinator preferences and behavioural constancy are all likely to con-tribute to the continued coexistence of R.acris and R.repens,despite apparent overlap in their pollination niches.Such differences have the potential to facilitate the maintenance of species diversity in plant com-munities,even where plants appear to share similar floral phenotypes.展开更多
文摘Aims Competition for pollinators between phenotypically similar flowers is believed to play an important role in floral trait diversification in the angiosperms.However,in many plant communities,species with apparently similar floral phenotypes and generalist pollina-tion systems co-flower.Here,the pollination systems of Ranunculus acris L.and Ranunculus repens L.were investigated to determine the factors enabling the species to coexist within apparently over-lapping pollination niches.Methods Sympatrically flowering populations of R.acris and R.repens were investigated at three study sites in West Wales.The flo-ral phenotypes of the two species were compared using meas-urements of floral morphology and spectral analyses of petal reflectance,using principal component analysis and bee and fly colour-space models.Evidence of inter-specific discrimina-tion by foraging insects was tested for in the field and using floral arrays.The relative roles of behavioural constancy and spatial patchiness in maintaining pollinator fidelity were estimated.Important Findings The floral phenotypes of R.acris and R.repens differed significantly.Social bees were highly constant when foraging at flowers of the two species and patchy floral distribution explained some of the observed fidelity.Dipterans visiting mixed floral arrays appeared to discriminate between the species,visiting more R.acris than R.repens flowers,but there was no difference in the number of vis-its to single-species arrays.Social bees were more likely to display constancy to flowers of R.repens in the field.Patchiness in floral distribution,subtle differences in floral phenotype,pollinator preferences and behavioural constancy are all likely to con-tribute to the continued coexistence of R.acris and R.repens,despite apparent overlap in their pollination niches.Such differences have the potential to facilitate the maintenance of species diversity in plant com-munities,even where plants appear to share similar floral phenotypes.
