  Nutrients from a flowering plant are shared by its pollinators, giving rise
to competition in the latter. Such exploitative competition of pollinators can
limit their abundance and affect the global organization of the mutualistic
partnership in the plant-pollinator mutualistic community. Here we investigate
the effects of the exploitative competition between pollinators on the
structure and the species abundance of the mutualistic networks which evolve by
changing mutualistic partnership towards higher abundance of species.
Simulations show different emergent network characteristics between plants and
animals; hub plants connected to many pollinators are very rare while a few
super-hub pollinators appear with the exploitative competition included, in
contrast to equally many hubs of both types without the exploitative
competition. More interestingly, the abundance of plant species increases with
increasing the exploitative competition strength. We analyze the inverse of the
generalized interaction matrix in the weak-interaction limit to identify the
leading structural factors relevant to the species abundance, which are shown
to be instrumental in optimizing the network structure to increase the
mutualistic benefit and lower the cost of exploitative competition.
