How exotic species integrate into pollination networks

Background/Question/Methods

There is increasing worldwide concern about the impact of introductions of exotic species on ecological communities. Since many exotic plants, for example, depend on native pollinators to successfully establish, it is of paramount importance that we understand precisely how exotic species integrate into existing communities. Recent studies of pollination networks---the network of mutually-beneficial interactions within a community of flowering plants and their animal pollinators---has uncovered multiple universal patterns in their structure. These structural patterns have consequently been shown to facilitate coexistence of greater numbers of species and to influence each constituent species' vulnerability to extinction.

In this talk, we characterize how exotic species integrate into pollination networks as well as the expected long-term consequences of this integration. To do so, we use a database of empirical pollination networks, covering distinct communities found across the globe, and systematically compare the properties of exotic plant species to their native counterparts.

Results/Conclusions

We find that, in terms of species-specific properties, exotic species are virtually indistinguishable from native species. For example, they neither tend to have fewer or more interactions than native species nor do they tend to be more or less phylogenetically related to species already present. Though the species themselves are not dissimilar, we do observe statistically-significant differences between the species with whom exotic species interact and those with whom they don't.

Intriguingly, and in contrast to earlier studies, the exotic species found across the different communities exhibit a stronger tendency to interact with specialist or moderately-specialist pollinators than they do with generalists. Additionally, exotic species tend to interact with pollinators whose intrinsic dynamics are most likely to lead to their extinction. Overall, our results indicate that a successful introduction into a pollination network depends more strongly on the composition of the invaded community than in the characteristics of the invading species.