Cooperative Network Dynamics

摘要

Nested, or hierarchically arranged, mutualisms allow ecosystems to support more species than they otherwise would. But in this and other contexts, the growth of such networks could carry a heavy price. On page 1018 of this issue, Bascompte and colleagues (Bastolla et al.) describe how they have followed up earlier studies of the mutualistic networks of plants and their animal pollinators. This new investigation is an intriguing enquiry into whether the particular topology of cooperative interactions accommodates greater biodiversity (network size), and it has potential applications beyond ecology to the dynamics of social and financial systems. In the ecological networks under consideration, plants and animals compete for resources within their respective groups. But they may obtain mutual pay-offs across groups, in the form of pollination services and nectar rewards, that can offset the dynamic limits to system size determined by competition. These 'dual category', or bipartite, cooperative networks exhibit a common architecture called nestedness2, in which relative specialists - those species with few cooperative links -interact only with subsets of species having greater numbers of cooperative links.