The frugivory network between birds and plants in a Neotropical periurban park

Frugivory networks exhibit a set of properties characterized by a number
of network-theory derived metrics. Their structure often form
deterministic patterns that can be explained by the functional roles of
interacting species. Although we know lots about how these networks are
organized when ecosystems are in a complete, functional condition, we know
much less about how incomplete and simplified networks (such as those
found in urban and periurban parks) are organized, which features are
maintained, which ones are not, and why. In this paper, we examine the
properties of a network between frugivorous birds and plants in a small
Neotropical periurban park. We found a frugivory network composed of 29
species of birds and 23 of plants. The main roles in this network are
played by four species of generalist birds (three resident, one migratory:
Myiozetetes similis, Turdus grayi, Chlorospingus flavopectus, and
Dumetella carolinensis) and three species of plants (one exotic, two early
successional: Phoenix canariensis, Phoradendron sp., and Witheringia
stramoniifolia). When compared to reference data from other locations in
the Neotropics, species richness is low, one important network-level
metric is maintained (modularity) whereas another one is not (nestedness).
Nestedness, a metric associated with network specialists, is a feature
this network lacks. Species-level metrics such as degree, species
strength, and module roles, are not maintained. Our work supports
modularity as the most pervasive network-level metric of altered habitats.
From a successional point of view, our results suggest that properties
revealed by species-level indices may be developed at a later time,
lagging the acquisition of structural elements.