Frequency dependence of pollinator visitation rates suggests that pollination niches can allow plant species coexistence

1. How do many species coexist within a trophic level? Resource niches are the classical answer, but in plants which share a small set of abiotic resources the possibilities for resource partitioning are limited. One possible explanation is that plant species have different pollination niches, with each species specialized to a subset of the available animal species. If this pollinator partitioning results in negative frequency dependence such that each plant species’ reproduction is reduced when it becomes abundant, pollination niches could maintain plant diversity, provided that the strength of negative frequency dependence is sufficient to overcome fitness inequalities between species. 2. We tested this idea by quantifying the effect of species relative abundance on pollinator visitation rate in a 7000 m² plot of South African Fynbos vegetation. In addition, we quantified the effect of intraspecific abundance variation at a smaller spatial scale (9 m² plots), documented species’ poll...