  We study how the community structure of bipartite mutualistic networks
changes in a dynamic context. First, we consider a real mutualistic network and
introduce extinction events according to several scenarios. We model
extinctions as node or interaction removals. For node removal, we consider
random, directed and sequential extinctions; for interaction removal, we
consider random extinctions. The bipartite network reorganizes showing an
increase of the effective modularity and a fast decrease of the persistence of
the species in the original communities with increasing number of extinction
events. Second, we compare extinctions in a real mutualistic network with the
growth of a bipartite network model. The modularity reaches a stationary value
and nodes remain in the same community after joining the network. Our results
show that perturbations and disruptive events affect the connectivity pattern
of mutualistic networks at the mesoscale level. The increase of the effective
modularity observed in some scenarios could provide some protection to the
remaining ecosystem.
