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| Mutualistic interaction networks have been shown to be structurally conserved over space
and time while pairwise interactions show high variability. In such networks, modularity is
the division of species into compartments, or modules, where species within modules share
more interactions with each other than they do with species from other modules. Such a
modular structure is common in mutualistic networks and several evolutionary and ecological
mechanisms have been proposed as underlying drivers. One prominent explanation is the
existence of pollination syndromes where flowers tend to attract certain pollinators as
determined by a set of traits. We investigate the modularity of seven community level plantpollinator
networks sampled in rupestrian grasslands, or campos rupestres, in SE Brazil.
Defining pollination systems as corresponding groups of flower syndromes and pollinator
functional groups, we test the two hypotheses that (i) interacting species from the same
pollination system are more often assigned to the same module than interacting species from
different pollination systems and, that (ii) interactions between species from the same
pollination system are more consistent across space than interactions between species from
different pollination systems. Specifically we ask 1) whether networks are consistently
modular across space, 2) whether interactions among species of the same pollination system
occur more often inside modules, compared to interactions among species of different
pollination systems, and finally, 3) whether the spatial variation in interaction identity, i.e.
spatial interaction rewiring, is affected by trait complementarity among species, as indicated
by pollination systems. We confirm that networks are consistently modular across space and
that interactions within pollination systems principally occur inside modules. Despite a strong
tendency, we did not find a significant effect of pollination systems on the spatial consistency
of pairwise interactions. These results indicate that the spatial rewiring of interactions could
be constrained by pollination systems, resulting in conserved network structures in spite of | |
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