Host-Parasite Networks: An Integrative Overview with Tropical Examples

Historically, the role of parasites in ecosystem functioning has been considered trivial because a cursory examination reveals that their relative biomass is low compared with that of other trophic groups. However there is increasing evidence that parasite-mediated effects could be significant: they shape host population dynamics, alter interspecific competition, influence energy flow and appear to be important drivers of biodiversity. Indeed they influence a range of ecosystem functions and have a major effect on the structure of some food webs. Here, we consider the bottom-up and top-down processes of how parasitism influences ecosystem functioning and show that there is evidence that parasites are important for biodiversity and production; thus, we consider a healthy system to be one that is rich in parasite species.

Integrative approaches to the study of complex systems demand that one knows the manner in which the parts comprising the system are connected. The structure of the complex network defining the interactions provides insight into the function and evolution of the components of the system. Unfortunately, the large size and intricacy of these networks implies that such insight is usually difficult to extract. Here, we propose a method that allows one to systematically extract and display information contained in complex networks. Specifically, we demonstrate that one can (i) find modules in complex networks and (ii) classify nodes into universal roles according to their pattern of within- and between-module connections. The method thus yields a 'cartographic representation' of complex networks.