Abstract

The angiosperms show remarkable floral diversity. However, the ecological processes involved in flower diversification remain poorly understood. In this article I propose that different species' floral abundances drive adaptation to different pollinators and promote different degrees of specialization. In this view, interspecific variability in abundance can foster floral diversification. I develop a mathematical model of pollen transfer considering the interaction of several pollination processes---pollen removal and carryover, intra- and interspecific competition for pollinator visitation, and interspecific pollen transfer---that are linked to floral abundance. To assess if and how floral abundance can generate floral diversity, I use the model to assemble plant-pollinator networks from simulated plant and pollinator communities. The model shows that evolution on highly specialized pollinators and pollinators with high pollen carryover capacity is favoured at low floral abundance, while evolution on more abundant pollinators is favoured at high floral abundance. Furthermore, floral specialization is favoured at low floral abundance, while generalization is favoured at high abundance. In simulated plant communities of variable floral abundance, different pollinator systems evolve among the different plant species. The model demonstrates a new mechanism by which floral diversity can be generated, contributing to our understanding of floral evolution and diversification.