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RESEARCH PRODUCT

Individual phenology and spatial heterogeneity shape plant reproduction through plant-pollinator interactions

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Plant-pollinator interactions condition the seed set of insect-pollinated plants. Pollination competition andfacilitation amongst co-flowering plants produce unequally distributed reproductive outcomes amongstplant species and individuals. Moreover, spatio-temporal heterogeneity in floral resources and plant traits(e.g. phenology) can modulate the plant-pollinator interactions, at different ecological scales, that a plantindividual is exposed to during its flowering period, with implications for pollination and seed set.Using a field experiment, we tested how multi-scale plant-pollinator interactions, modulated by floweringphenology and spatio-temporal floral heterogeneity (arising from agroecological infrastructure) combined toaffect the seed set of individual wild plant species. We transplanted replicates of insect-pollinated plantspecies contrasting in flowering phenology, Cyanus segetum and Centaurea jacea (Asteraceae), into sownwildflower or legume-grass field borders across a farm-scale agroecological experiment. We recorded theflowering period of each individual plant, the corresponding plant-pollinator interactions at individual, localcommunity and agroecosystem-scales, and the subsequent seed production.Our phenologically constrained models of C. segetum/C. jacea seed set revealed that the individual plantattractiveness (integrating floral display and visitation rate), the local plant-insect community composition(richness or density) and the size and architecture of the agroecosystem-scale plant-pollinator networkcombined in specific ways for each focal species to influence seed set. For C. segetum, competition andfacilitation between the focal individuals and other plant species co-existed at the local floral communityscale, with the net balance conditioned by the position of C. segetum in the agro-ecosystem scale interactionnetwork. For C. jacea, facilitation of seed set dominated at the community scale through the combination ofindividual attractiveness and the community floral density.Individual plant seed set was thus shaped by patterns in diversity and network structure that imply a cooccurrence of pollinator-mediated facilitative and competitive interactions operating within and betweenecological scales.