Exploring the mechanisms that are modeling the interaction between hummingbirds and their nectar resources using network analysis
Mutualistic interactions as pollination have been considered as the paradigm that explain and sustain the biodiversity of the earth, because these processes create a complex network of interacting species that vary in the pattern of the connections and the strength of their interactions. In the present work we constructed a mutualistic network based on visits, to analyze the pattern of interaction between hummingbirds (Aves: Trochilidae) and their nectar resources at the family and continental scales. Due to the fact that this network is based on mutualistic interactions, we predicted that the network was: 1) highly heterogeneous, 2) nested and 3) had compartments or modules. Likewise, to interpret this network from the evolutive and geographic perspective, we tested two hypotheses: First, that reciprocal selection between hummingbirds and plants reshapes permanently the traits and life histories of the two groups, favoring generalization. Second, that the number and pattern of connections in a net are the consequence, among other things, of the effect of the altitude, biogeographical region and niche conservatism of the species that are connected to it.
The full hummingbird-plant interaction network included 4556 links between 293 hummingbird species and 1305 plant species. This network was as other mutualistic networks: nested, heterogeneous and compartmentalized. When we tested the biogeographical and evolutive hypothesis, it was clear that the interaction pattern of this net was modelled principally by the biogeographical origin of the nodes and the morphology of hummingbirds and plants used by them as nectar resources.