LAUSR

PREMISE OF THE STUDY The role of pollinators in evolutionary floral divergence has spurred substantial effort into measuring pollinator-mediated phenotypic selection and its variation in space and time. To estimate pollinator-mediated selection it is necessary to separate the fitness consequences of pollination processes from other factors affecting fitness. METHODS We build a fitness function linking phenotypic traits of food-deceptive orchids to female reproductive success by including pollinator visitation and pollen deposition as intermediate performance components and used the fitness function to estimate pollinator-mediated selection through female reproductive success. We also considered male performance quantified as pollinarium removal and assessed similarity in trait effects on male and female performance. KEY RESULTS The proportion of plants visited at least once by an effective pollinator was moderate to high, ranging from 53.7% to 85.1%. Tall, many-flowered plants were often more likely to be visited and pollinated. Given effective pollination, pollen deposition onto stigmas tended to be more likely for taller plants. Pollen deposition further depended on traits affecting the fit of pollinators to flowers (flower size, spur length), though the exact relationships varied in time and space. Using the fitness function, we detected pollinator-mediated selection through female reproductive success acting on multiple traits, and that selection varied detectably among taxa after accounting for sampling uncertainty. Across taxa, selection on most traits was both stronger on average and more variable when pollination was less reliable. CONCLUSIONS These results support pollination-related trait-performance-fitness relationships, and thus pollinator-mediated selection on traits functionally involved in the pollination process. This article is protected by copyright. All rights reserved.