How Foraging Behaviour and Resource Partitioning Can Drive the Evolution of Flowers and the Structure of Pollination Networks

Many flowers are visited by a large array of pollinators, often belonging to different taxonomic groups, and many pollinator species visit a wide array of flowers with different morphologies. This observation has led pollination ecologists to question the role played by pollinators in flower diversification and the extent to which floral similarities reflect convergent evolution to specific pollinator assemblages rather than other factors, such as phylogenetic constraints. In this paper, we review several ecological and evolutionary models that help to explain how pollinators can play a key role in floral evolution despite heterogeneities in plant-pollinator interactions. Our basic tenant is that, in animal pollinated species, the trajectory of pollen grains is determined by the foraging strategy of pollinators. Starting from a first approximation based on optimal foraging theory, ecological models related to the principles behind the ideal free distribution can be used to predict differences in floral and pollinator traits that will lead to resource partitioning. Building upon these results, evolutionary models based on game theory can be used to predict changes in traits of flowers and pollinators. These models show that pollinators can drive the evolution of floral divergence in the presence of behavioural noise and temporal variability in the composition of pollinator ensembles.