  Evolutionary transitions among ecological interactions are widely known,
although their detailed dynamics remain absent for most population models.
Adaptive dynamics has been used to illustrate how the parameters of population
models might shift through evolution, but within an ecological regime. Here we
use adaptive dynamics combined with a generalised logistic model of population
dynamics to show that transitions of ecological interactions might appear as a
consequence of evolution. To this purpose we introduce a two-microbial toy
model in which population parameters are determined by a bookkeeping of
resources taken from (and excreted to) the environment, as well as from the
byproducts of the other species. Despite its simplicity, this model exhibits
all kinds of potential ecological transitions, some of which resemble those
found in nature. Overall, the model shows a clear trend toward the emergence of
mutualism.
