Simple bit of biology gives insight into complex ecosystems

Frank van Veen and co-workers show that it is possible to predict the connectivity of ecosystems simply from the feeding mode of their component species.

A food web is the network of who eats whom in an ecosystem. The extent to which the species within such a network are connected to each other via feeding links is an important factor in determining how the ecosystem will respond to environmental change. In a recent study published in the Journal of Animal Ecology, Frank van Veen and co-workers showed that it is possible to predict this connectivity simply from the feeding mode of species. They compared the food webs of aphids (plant sap feeding insects, 29 species) and three types of natural enemies: predators (ladybirds etc., 13 species), fungal pathogens (5 species) and parasitic wasps (24 species). Because of the increasing intimacy of the interaction between aphid and natural enemy from predator, via pathogen to parasitoid, the researchers expected the latter to be most specialised. They show that this is indeed the case and that the predator web is ten times more connected than the parasitoid web, while the pathogen web is intermediate.

Ecologists have long searched for a universal rule of what determines connectivity and other patterns in food webs, often far removed from biology. This work shows the importance of basic biological information to the understanding of how ecosystems are organised and thus ultimately how they will respond to environmental change.

Contact: Frank van Veen (f.vanveen@imperial.ac.uk)

Food web structure of three guilds of natural enemies: predators, parasitoids and pathogens of aphids. Journal of Animal Ecology, January 2008
doi: 10.1111/j.1365-2656.2007.01325.x

FJF VAN VEEN (1,2), CB MÜLLER (2,4), JK PELL(3) & HCJ GODFRAY (1,2,5)
(1) NERC Centre for Population Biology and (2) Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berks. SL5 7PY, UK
(3) Plant and Invertebrate Ecology Division, Rothamsted Research, Harpenden, Herts. AL5 2JQ UK.
(4) Present address: Institute of Environmental Sciences, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
(5) Present address: Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, U.K.