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Nested architecture in ecological networks explained

A random network with 1000 nodes and 1000 links

A random network with 1000 nodes and 1000 links. Although the possible number of links is nearly 50000, a merely 2% of randomly generated links (1000 links) can already connect all the nodes in one cluster (credit: C. Hui).

The architecture of ecological networks is one of the most important research priorities in ecology. Its importance is shown if you search the word ‘networks’ on Google Scholar. For instance, Barabasi et al.ís (1999) paper in network scaling in Science has been cited more than 9000 times. Watts et al.ís (1998) Nature paper on small-world networks has been cited more than 13000 times. Newmanís (2003) SIAM Review paper on network structure has been cited nearly 6000 times. Albert & Barabasiís (2002) Reviews on Modern Physics paper on statistical mechanics of complex networks has been cited more than 8000 times.

In their 2003 PNAS paper, Bascompte et al. reported the distinctive feature of nestedness in many plant-animal mutualistic networks, such as in pollination and seed dispersal communities. However, an integrative and quantitative explanation for the importance of networks has been lacking. Because mutualistic interactions are crucial for sustaining ecosystem functioning and services, generate biodiversity, and affect community stability, it is important to reveal the potential mechanisms behind this particular structure in many ecological networks.

Scientists from the C·I·B recently presented the first mathematical model to explain the rise of nestedness in ecological networks. Besides fitting remarkably well with observations from 81 empirical networks, their model also explained four well known patterns in mutualistic networks and even structures in antagonistic networks, such as predator-prey networks and food webs. Importantly, they demonstrated that a mutualistic network converges from an initial random network to a nested network with an intrinsic stable level of nestedness, suggesting that the observed nested architecture could depend solely on the physical features of the network. Biological and ecological patterns in this regard only reflect the physical features of adaptive networks.

Read the paper:

Zhang, F., Hui, C. & Terblanche, J.S. (2011) An interaction switch predicts the nested architecture of mutualistic networks. Ecology Letters, Online Early.