Pollinator-mediated facilitation alleviates pollen limitation through effects on the quality of plant reproduction

Facilitation and competition among plants sharing pollinators have contrasting consequences for each species' fitness. However, it is unclear whether pollinator-mediated indirect interactions between plants affect plant fitness in a multispecies context. Here, we investigated how pollinator sharing affects pollen limitation (contribution of pollination to fitness) in a tropical hummingbird-pollinated community marked by facilitation. We employed indices describing how much a plant species is important to shared pollinators (acting degree) and have its shared pollinators influenced by other plants (target degree) within the plant-hummingbird network. Since facilitation often increases pollination quantity but not necessarily quality, we expected both indices to be associated with reductions in pollen limitation estimates that depend on pollination quantity (fruit set and seed number) rather than estimates more strictly related to quality (seed weight and germination). Instead, we found t...