Comparing bird-plant interaction networks between xerophytic and humid forests of the southeastern Neotropics

Abstract

Frugivorous birds play a key role by influencing the distribution and evolution of plant communities worldwide. Despite their importance, comparative studies on bird frugivory remain limited in several neotropical regions, leaving a significant gap in our understanding of this vital ecological process. Our objective was to determine the frugivorous bird ensembles, their food plants, and the resulting interaction networks, of two previously understudied, contiguous and contrasting, regions in the southeastern Neotropics: the Chaco Forest and the Parana Forest in Argentina. Through mist-netting and transects adapted for frugivory we recorded that the Chaco network consisted in 32 frugivorous bird species and 27 orni- thochorous plant species, with a 415 interaction frequency (IF) value, and 118 number of links (NOL). The Parana network consisted in 27 bird species and 28 plant species, with a 592 IF value and 109 NOL. Although bird assemblages were similar, network metrics (connectance, modularity, specialization, nestedness and niche overlap), and interaction patterns showed differences between the networks, as well as the composition of plant species, also, a heterogeneous structure of modules was found. Thraupidae, Turdidae and Tyrannidae bird families showed the highest degree of interaction. These families might be influencing the capacity of forest regeneration and the maintenance of interaction networks due to their roles in the networks and through seed dispersal.