Figure 1. Importance of different pollination processes for plant pollination success as a function of floral abundance, as determined by the mathematical model. Comparison of pollination success expected for low, medium and high values of A) pollinator abundance, B) pollinator specialization, C) pollen removal and D) carryover at variable floral abundance (see Table 1 for parameter values). E) Importance of the quantity component of pollination, represented by pollinator abundance, and the quality component, determined by pollinator specialization and carryover as a function of floral abundance (measured as the average between the importance of pollinator specialization and carryover). F) Hypothetical representation of the pollination systems offering the highest pollination success at different floral abundance. Specialization on pollinators with high pollen carryover and level of specialization is favoured at low floral abundance (hypothetical examples; hawkmoths and hummingbirds). At intermediate abundance, specialized pollination by more abundant pollinators (hypothetical example; bees) is favoured. At high floral abundance, most pollinators are not sufficiently abundant to remove most pollen grains and generalization becomes more advantageous. When floral abundance is too high for the pollinator community to remove most pollen grains, reliance on abiotic pollen vectors is expected.
Figure 2. Plant-pollinator networks resulting from simulated communities of different plant species and pollinator attributes. A, B) Plant-pollinator networks formed with plant species of variable floral abundance result in variable levels of generalization among plant species. C, D) Networks composed entirely of low-abundance plant species result in high level of specialization. E, F) Networks composed entirely of high-abundance plant species result in widespread generalization. G, H) Networks composed of low-abundance plant species that interact with a pollinator community composed of functionally similar pollinators result in specialization and niche partitioning among plant species for the use of the different pollinators. In A, C, E and G, the thickness of the links represents the number of visits of a pollinator to a plant species. In B, D, F and H, grey squares denote interaction between a plant and a pollinator and darker shades represent higher frequencies of interaction.
Figure 3. Degree of generalization and attributes of the pollinators on which a plant species colonizing simulated plant communities evolved as a function of its floral abundance. The parameter values represent the average values of pollen carryover capacity, specialization and abundance of the pollinators on which the new colonist evolved and degree of floral generalization of the new colonist. The parameter values on the y-axis were normalized so that the minimum value corresponds to 0 and the maximum value corresponding to 1. The standard error of the mean parameter values among the 100 simulations is presented as the shaded area around the mean values.