  As impacts of introduced species cascade through trophic levels, they can
cause indirect and counter-intuitive effects. To investigate the impact of
invasive species at the network scale, we use a generalized food web model,
capable of propagating changes through networks with a series of ecologically
realistic criteria. Using data from a small British offshore island, we
quantify the impacts of four virtual invasive species (an insectivore, a
herbivore, a carnivore and an omnivore whose diet is based on a rat) and
explore which clusters of species react in similar ways. We find that the
predictions for the impacts of invasive species are ecologically plausible,
even for large networks robust predictions for the impacts of invasive species
can be obtained. Species in the same taxonomic group are similarly impacted by
a virtual invasive species. However, interesting differences within a given
taxonomic group can occur. The results suggest that some native species may be
at risk from a wider range of invasives than previously believed. The
implications of these results for ecologists and land managers are discussed.
