other structural features of food webs, this should
be a priority research question about community
topology.
It would be fascinating to see whether the addi-
tion of weak interactors can stabilize food chains,
and whether those effects offset destabilizing
effects of increased energy inputs, as some theories
predict (McCann et al.1998). Observations and
models on soil food webs indeed suggest that this
is the case (Neutelet al.2002).22 SHAPE AND STRUCTURE