  Ecosystems dynamics is often considered as driven by a coupling of species'
resource consumption and its population size dynamics. Such resource-population
dynamics is captured by MacArthur-type models. One biologically relevant
feature that would also need to be captured by such models is the introduction
of new and different species. Speciation introduces a stochastic component in
the otherwise deterministic MacArthur theory. We describe here how speciation
can be implemented to yield a model that is consistent with current theory on
equilibrium resource-consumer models, but also displays readily observable rank
diversity metric changes. The model also reproduces a priority effect. Adding
speciation to a MacArthur-style model so provides an attractively simple
extension to explore the rich dynamics in evolving ecosystems.
