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| Complex networks of species interactions might be determined by species traits but also by simple chance meetings governed by species
abundances. Although the idea that species traits structure mutualistic networks is appealing, most studies have found abundance to be
a major structuring mechanism underlying interaction frequencies. With a well-resolved plant–hummingbird interaction network from
the Neotropical savanna in Brazil, we asked whether species morphology, phenology, nectar availability and habitat occupancy and/or
abundance best predicted the frequency of interactions. For this, we constructed interaction probability matrices and compared them to
the observed plant-hummingbird matrix through a likelihood approach. Furthermore, a recently proposed modularity algorithm for
weighted bipartite networks was employed to evaluate whether these factors also scale-up to the formation of modules in the network.
Interaction frequencies were best predicted by species morphology, phenology and habitat occupancy, while species abundances and nec-
tar availability performed poorly. The plant–hummingbird network was modular, and modules were associated to morphological special-
ization and habitat occupancy. Our ?ndings highlight the importance of traits as determinants of interaction frequencies and network
structure, corroborating the results of a previous study on a plant–hummingbird network from the Brazilian Atlantic Forest. Thus, we
propose that traits matter more in tropical plant–hummingbird networks than in less specialized systems. To test the generality of this
hypothesis, future research could employ geographic or taxonomic cross-system comparisons contrasting networks with known differ-
ences in level of specialization | |
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