Resource partitioning through flexible foraging results in modular plant-pollinator interaction networks
In plant-pollinator interaction networks, foraging choices by pollinators help form the connecting links between species. As a result, flexibility in foraging choices may play an important role in determining the topology of interaction networks. Adaptive flexibility can allow pollinators to switch foraging targets in response to factors such as the presence of competitors or the relative abundance of resources. However, even though pollinators are highly flexible in floral resource use, flexible foraging is rarely considered in studies of plant-pollinator networks (or ecological networks in general). To understand how flexible foraging affects network structure we examined differences between locally realized interactions and the sets of potential interactions within 25 weighted plant-pollinator networks in two different regions of the USA.
We found that realized connectance was much lower than potential connectance, indicating a local narrowing of diet breadth. Moreover, the foraging choices pollinators made – which particular plant species to visit and at what rates – resulted in networks that were significantly less nested and significantly more modular and specialized than networks of potential interactions. The emergence of modularity and network-level specialization through flexible foraging may result from resource partitioning. The degree of partitioning increases simultaneously with the number of competing pollinator and plant resource species, a behavior known to promote community stability.