Variation in neighbourhood context shapes frugivore-mediated facilitation and competition among co-dispersed plant species

1. 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 p...