Ecological networks of interacting species acquire complexity and robustness through a long process of adaptation where consumers become increasingly specialized on dependable resources. This simple mechanism explains why specialization is so common in natural systems, despite the fact that intuition would suggest that specialized consumers, such as parasites with narrow host ranges, are the most likely candidates to go co-extinct. In fact, empirical and simulated data demonstrate that, if a consumer’s co-extinction risk is quantified as a function of both its specialization and of the dependability of its resources, then specialized consumers are not more vulnerable than generalist ones, which may also be part of the solution to the complexity-stability paradox. This, however, holds true only when the resources’ dependability values do not change over time (i.e. remain the same as those that were in place while complexity evolved). Even slight modifications in resources’ dependability can disrupt the co-evolved robustness, making robust ecological networks as fragile as under the simplified assumption that specialization alone drives co-extinction risk.
Results/Conclusions
By focusing on both real world and ‘digital’ host-parasite networks, I will demonstrate how human activity has altered natural ecosystems (and, in turn, the relative vulnerability of free-living species) so much that it makes the structure of resource-consumer networks obsolete in the Anthropocene.