  Simulations of the coevolution of many interacting species are performed
using the Webworld model. The model has a realistic set of predator-prey
equations that describe the population dynamics of the species for any
structure of the food web. The equations account for competition between
species for the same resources, and for the diet choice of predators between
alternative prey according to an evolutionarily stable strategy. The set of
species present undergoes long-term evolution due to speciation and extinction
events. We summarize results obtained on the macro-evolutionary dynamics of
speciations and extinctions, and on the statistical properties of the food webs
that are generated by the model. Simulations begin from small numbers of
species and build up to larger webs with relatively constant species number on
average. The rate of origination and extinction of species are relatively high,
but remain roughly balanced throughout the simulations. When a `parent' species
undergoes speciation, the `child' species usually adds to the same trophic
level as the parent. The chance of the child species surviving is significantly
higher if the parent is on the second or third trophic level than if it is on
the first level, most likely due to a wider choice of possible prey for species
on higher levels. Addition of a new species sometimes causes extinction of
existing species. The parent species has a high probability of extinction
because it has strong competition with the new species. Non-parental
competitors of the new species also have a significantly higher extinction
probability than average, as do prey of the new species. Predators of the new
species are less likely than average to become extinct.

Adaptation and Self-Organizing Systems;Condensed Matter;Populations and Evolution