  We investigate the long-term web structure emerging in evolutionary food web
models when different types of functional responses are used. We find that
large and complex webs with several trophic layers arise only if the population
dynamics is such that it allows predators to focus on their best prey species.
This can be achieved using modified Lotka-Volterra or Holling/Beddington
functional responses with effective couplings that depend on the predator's
efficiency at exploiting the prey, or a ratio-dependent functional response
with adaptive foraging. In contrast, if standard Lotka-Volterra or
Holling/Beddington functional responses are used, long-term evolution generates
webs with almost all species being basal, and with additionally many links
between these species. Interestingly, in all cases studied, a large proportion
of weak links result naturally from the evolution of the food webs.
