Can pollination niches facilitate plant coexistence?

The question of why there are so many plant species needs two kinds of answer: an explanation for the origin of plant species, and an explanation for how they can coexist. Pollinators are often implicated in the origin of plant species because adaptation to different modes of pollination can drive divergence in floral traits and bring about reproductive isolation. However, very few studies have attempted to answer the next question: 'Can plant species that differ only in their mode of pollination coexist?' Fragmentary evidence supports the idea that intraspecific competition for pollination resources can limit population growth rate, thus allowing the coexistence of species that use different pollinators, or the same pollinators at different times.