  Ecological systems are emergent features of ecological and adaptive dynamics
of a community of interacting species. By natural selection through the abiotic
environment and by co-adaptation within the community, species evolve, thereby
giving rise to the ecological networks we regard as ecosystems. This
reductionist perspective can be contrasted with the view that as species have
to fit in the surrounding system, the system itself exerts selection pressure
on the evolutionary pathways of the species. This interplay of bottom-up and
top-down control in the development and growth of ecological systems has long
been discussed, however empirical ecosystem data is scarce and a comprehensive
mathematical framework is lacking. We present a way of quantifying the relative
weight of natural selection and coadaptation grounded in information theory, to
assess the relative role of bottom-up and top-down control in the evolution of
ecological systems, and analyse the information transfer in an individual based
stochastic complex systems model, the Tangled Nature Model of evolutionary
ecology. We show that ecological communities evolve from mainly bottom-up
controlled early-successional systems to more strongly top-down controlled
late-successional systems, as coadaptation progresses. Species which have a
high influence on selection are also generally more abundant. Hence our
findings imply that ecological communities are shaped by a dialogue of
bottom-up and top-down control, where the role of the systemic selection and
integrity becomes more pronounced the further the ecosystem is developed.
