Mesoscale network properties in ecological system models

Network models are among the most powerful tools in systems ecology. As trophic relationships (i.e. who eats whom) are among the most frequent interspecific interactions, food webs serve well as system models. To better understand ecosystem dynamics, neither strictly local (focusing on individual species) nor strictly global (focusing on the whole ecosystem) approaches are adequate. This mesoscale view on network links suggests to quantify indirect interactions up to some reasonable range, and a mesoscale view on network nodes suggests to identify a small set of nodes that are in the most important network positions. We present some examples taking this mesoscale view in ecosystem modeling and use these to discuss the mesoscale perspective. For systems-based conservation management, we suggest to focus on keystone species complexes that are determined considering their indirect interaction neighborhood. This approach provides a systems-based alternative that hopefully increases the efficiency of future conservation efforts: A small set of system components are targeted in such a way that a large set of the remaining elements are benefited.