Summary1. Co-occurring and simultaneously fruiting plant species may either compete for dispersal by shared frugivores or enhance each other's dispersal through joint attraction of frugivores. While competitive plant-plant interactions are expected to cause the evolutionary divergence of fruit phenologies, facilitative interactions are assumed to promote their convergence. To which extent competitive and facilitative interactions among plant species with similar phenological niches are controlled by spatial variation in their local abundance and co-occurrence is poorly understood. 2. Here, we test the hypotheses that when a plant species fruits in high densities, large phenological overlap with other plant species causes competition for seed dispersers owing to frugivore satiation. Conversely, we expect large phenological overlap to enhance the dispersal of a plant species fruiting in low densities through attraction of frugivores by other species in its local neighbourhood. 3. We test these predictions on plant-frugivore networks based on seed removal from 15 woody, fleshy-fruited plant species by 30 avian and 4 mammalian frugivore species across 13 study sites in Białowie_ za Forest, Poland. 4. A null model indicated that fruit phenologies of the regional plant assemblage were more differentiated than expected by chance. In the local networks, the tendency of plants to share frugivores increased with phenological overlap. High phenological overlap reduced the seed removal rates, interaction strength (proportion of interactions) and the number of partners of plant species fruiting in high densities. Conversely, plant species fruiting in low densities mainly profited from high phenological overlap with other species. Importantly, the sharing of mutualistic partners among cofruiting plant species was also reflected in their co-occurrence. 5. Synthesis. Our study highlights that, in spite of the overall signal of competition, frugivore-mediated interactions among cofruiting plant species may consistently promote the establishment and persistence of rare species through facilitation. In addition, our results suggest that, among other factors, indirect coupling of species through shared mutualistic partners might be an important determinant of plant community assembly. The coupling through shared mutualists may cause the formation of associations among co-dispersed plant species and might contribute to the coexistence of species in plant-animal mutualistic communities.

Abstract. Plant reproductive success is often the outcome of mutualistic and antagonistic plant-animal interactions, which can be moderated by landscape composition. Studies addressing single plant-animal interactions are common, but studies simultaneously considering multiple plant-animal interactions in a landscape context are still scarce. We selectively excluded flower-visiting insects on phytometer plants and quantified how mutualistic and antagonistic interactions shaped the reproductive success of a common annual plant, wild mustard (Sinapis arvensis). Floral herbivory by larvae of rape pollen beetles (Meligethes spp.) strongly reduced fruit production, but could be minimized by insecticide application. Total seed production (the product of fruit production and seeds per fruit) strongly increased with pollinator visitation. On average, pollinator access to plants enhanced seed numbers by 754%. Insecticide treatment almost redoubled this number. The landscape composition (proportion of semi-natural habitats in 1000 m radius) surrounding phytometer plants did not affect plant-animal interactions, presumably due to the high dispersal ability of both the pollen beetles and the major pollinators (syrphid flies, bumblebees). In conclusion, pest control increased reproductive success only in the case of sufficient pollination.