Finding the rules that govern the stability of ecological systems is one of the most longstanding research topics of ecology, and as relevant today as when Elton and McArthur first postulated their hypotheses about the positive influence of complexity on stability. After May showed in the 70s, that complexity in and of itself does not confer (local) stability, but rather the opposite, the hunt has been on to find the aspects of ecological community structure that would allow for stability in complex systems.
Ecological communities are structured into discrete species guilds, such as plants, herbivores, and pollinators. This fundamental aspect of ecological communities has largely been missing from studies of local stability. Here, we ask whether the guild structure of ecological communities is one of the missing factors that stabilize complex communities.
We investigate the local stability, resilience, and reactivity of community matrices with and without guild structure, for mutualistic, competitive, and trophic interactions. When guild structure is present, the community matrices represent bipartite (i.e. two guild) interaction networks, with interactions structured into within- and between-guild interactions, e.g. in a mutualistic network, plants and pollinators interact mutualistically between guilds and compete within guilds.
Results/Conclusions
Results are preliminary, but suggest that the effect of guild structure on stability depends on the interaction type. Guild structure stabilized trophic communities; it increased local stability and resilience, and decreased reactivity. The opposite was observed for purely competitive communities. Mutualistic communities showed the most complex response to guild structure; whether guild structure was stabilizing or not, depended on how interactions within guilds were organized (see separate talk by Berry Brosi in session Predictive Network Ecology: Mutualism, Evolution and Ecosystem Services).
Previous studies of local stability of ecological communities have either not included realistic network structure, such as guild structure, or have showed that realistic network structure decrease stability. We show that guild structure affect multiple aspects of community stability, and argue that realistic interaction structure stabilizes mutualistic communities and food webs.