Coevolution and the assembly of ecological networks

Background/Question/Methods

One of the major challenges for evolutionary biology is to understand how species coevolve and shape complex networks of interacting species. Several topological features of networks, including the nestedness, modularity and phylogenetic structure of interactions are believed to be affected by coevolution, but there has been no test whether these structures can be uniquely attributed to coevolution. Here we compare the network structure of bipartite
networks generated under different modes of coevolution. 

Results/Conclusions

We find that coevolution leaves a weak signal on network topology and,
furthermore, that the signal is not consistent across different modes of coevolution or for different ecological mechanisms that govern species interactions. For example, when interactions were based on matching between the traits of the resource species and the resource-seeking species, evolutionary communities that coevolved and co-speciated were, on average, more modular. In contrast, those communities were nested and not modular when the resource-seeking species needed to overcome an exploitative barrier in order to interact with the resource species. Finally, we find that the coevolutionary signal on network topology was easily obscured by species abundances and sampling. Our findings indicate that caution should be taken when using the network metrics to make inferences about the processes underlying the evolutionary history of a community.