Resistance and resilience of pollination networks to simulated invasions depend on adaptive foraging, network structure and the invaders' traits
The invasion of alien species into native ecosystems constitutes one of the major anthropogenic threats to the function and integrity of pollination systems. However, ecologists lack a clear understanding of factors driving invasion success and subsequent effects on the invaded ecosystems. Here, we use an integrative model of adaptive and nonlinear population dynamics to search for characteristics of alien species and network structures of native communities that drive invasion success and effects on native ecosystems. We simulated the introduction of plant and animal species with different traits into 1,200 networks with different levels of richness (15-238 species), connectance (0.04-0.34) and nestedness (NODFst 0.036-4.8). We then determined which among 21 structural properties of the networks best explained our results.
Animal invaders were always successful while plant invaders with parameters within the parameter range of natives were successful in <3% of their attempts. Larger networks with more links per animal species better resisted plant invasions and adaptive foraging helped native pollinators resist the impacts of animal invasions. Animal invaders that visit many more flowers per unit time than natives strongly decreased the abundance of native pollinators. Plant invaders that produce much more floral rewards than natives were very successful. Plant invaders that produced much more pollen than natives strongly decreased native plants' pollination events and abundances. These and other results demonstrate how factors such as the traits of invaders, the network structure of native communities, and the adaptive behavior of native pollinators, both alone and in concert, may drive the resistance, resilience, and sensitivity of pollination systems to invasions.