  We introduce and study a model of an interacting population of agents who
collaborate in groups which compete for limited resources. Groups are formed by
random matching agents and their worth is determined by the sum of the efforts
deployed by agents in group formation. Agents, on their side, have to share
their effort between contributing to their group's chances to outcompete other
groups and resource sharing among partners, when the group is successful. A
simple implementation of this strategic interaction gives rise to static and
evolutionary properties with a very rich phenomenology. A robust emerging
feature is the coexistence in the population of agents who invest mainly in the
success of their group and agents who concentrate in getting the largest share
of their group's profits.
