Understanding a “network of networks”

Understanding interactions between ecological networks is key to understanding how ecosystems respond to change

Any given ecosystem includes many different kinds of ecological networks such as food webs, plant-pollinator, plant-disperser and host-parasite networks. While recent research has detailed the workings of each of these networks individually, the interactions among these networks is much less known. In a first-of-its-kind study, Pocock and co-authors examined a “network of networks” in a 125 ha farm in the United Kingdom, which has been maintained organically and has been the focus of agri-environment management.

Over a period of 2 years, Pocock and colleagues recorded 1,501 interactions among 560 species of plants and animals on the farm. The animals recorded included pollinators and dispersers such as birds and butterflies (bio-indicators), a variety of parasitoid insects and predators such as spiders and beetles. Therefore, the interactions included were part of linked trophic, mutualistic and parasitic networks linked in a diverse agri-ecosystem.

In order to understand the resilience of the ecosystem to change, Pocock and colleagues used computer simulations to examine the removal of plant taxa and its consequences on different animal groups. They found certain groups such as pollinators were particularly susceptible to plant removal, while others such as parasitoids were more resilient to simulated plant extinctions. In general, an important finding to emerge from this study is that the responses of different functional groups of animals were not congruent, i.e. different animal groups showed varied responses to the same simulated change. This finding has important implications for restoration measures because the same measure might benefit one kind of species but might harm another. The study also identifies 27 “keystone” plant species whose removal is likely to have the largest impacts on the study system.

Further reading
Pocock MOJ, DM Evans & Jane Memmott. 2012. The robustness and restoration of a network of ecological networks. Science 335:973-977. doi: 10.1126/science.1214915

Photograph: Erica Marshall of muddyboots.org

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2012 Dec