Aims Pollinators are traditionally considered to be the primary agent of selection on floral traits.However,floral traits may also be under selection from abiotic agents(e.g.rain),which makes considering the relative ...Aims Pollinators are traditionally considered to be the primary agent of selection on floral traits.However,floral traits may also be under selection from abiotic agents(e.g.rain),which makes considering the relative importance of pollinators and abiotic selective agents on floral traits essential.The functional significance of floral orien-tation is often ascribed to pollinator attraction,but orientation can also protect reproductive structures from rain.Therefore,a study that incorporates both factors will enhance our understanding of the ecological roles of floral orientation in plant fitness.Mertensia brevistyla and M.fusiformis are herbaceous species that differ in their floral orientations.A series of field and laboratory experi-ments was used to investigate the adaptive function of floral orien-tation in these species,particularly with respect to pollinators and rain.Methods We measured and compared floral orientation and visitor assem-blages between M.brevistyla and M.fusiformis populations in west-ern Colorado,USA.We manipulated floral stems and conducted a choice experiment with floral visitors,and also compared orienta-tions of pollinator-visited stems with those of unvisited stems in a natural setting.We examined pollinator-and rain-mediated selec-tion on floral orientation by manipulating orientation,conducting supplemental pollinations,applying watering treatments and meas-uring subsequent seed set.We also experimentally tested the like-lihood of rain contact with anthers,and the effect of rainwater on pollen germinability.Important Findings Mertensia brevistyla had a significantly more upright floral orienta-tion than M.fusiformis,and seed set was highest in upright M.bre-vistyla and in horizontal/pendant M.fusiformis stems,supporting an adaptive function(via female fitness)of the interspecific difference in orientation.However,floral visitor assemblages did not differ significantly between the two species;visitors did not exhibit sig-nificant preference for either orientation;and pollinator-mediat展开更多
文摘Aims Pollinators are traditionally considered to be the primary agent of selection on floral traits.However,floral traits may also be under selection from abiotic agents(e.g.rain),which makes considering the relative importance of pollinators and abiotic selective agents on floral traits essential.The functional significance of floral orien-tation is often ascribed to pollinator attraction,but orientation can also protect reproductive structures from rain.Therefore,a study that incorporates both factors will enhance our understanding of the ecological roles of floral orientation in plant fitness.Mertensia brevistyla and M.fusiformis are herbaceous species that differ in their floral orientations.A series of field and laboratory experi-ments was used to investigate the adaptive function of floral orien-tation in these species,particularly with respect to pollinators and rain.Methods We measured and compared floral orientation and visitor assem-blages between M.brevistyla and M.fusiformis populations in west-ern Colorado,USA.We manipulated floral stems and conducted a choice experiment with floral visitors,and also compared orienta-tions of pollinator-visited stems with those of unvisited stems in a natural setting.We examined pollinator-and rain-mediated selec-tion on floral orientation by manipulating orientation,conducting supplemental pollinations,applying watering treatments and meas-uring subsequent seed set.We also experimentally tested the like-lihood of rain contact with anthers,and the effect of rainwater on pollen germinability.Important Findings Mertensia brevistyla had a significantly more upright floral orienta-tion than M.fusiformis,and seed set was highest in upright M.bre-vistyla and in horizontal/pendant M.fusiformis stems,supporting an adaptive function(via female fitness)of the interspecific difference in orientation.However,floral visitor assemblages did not differ significantly between the two species;visitors did not exhibit sig-nificant preference for either orientation;and pollinator-mediat
