Networks of seed dispersal by birds in the Espinal ecoregion, Córdoba, Argentina

Abstract

Studying frugivorous interactions in the context of broad networks is essential to understanding and evaluating the responses of ecosystems to different disturbances. The objective of this work was to determine the bird species that disperse seeds in the Espinal forest, to study which species of seeds are being dispersed, to establish if the seeds are dispersed without physical damage (legitimate dispersal) and to describe the interaction network generated. To do this, monthly sampling of birds was carried out with mist nets, and fecal samples were taken then were analyzed under a stereoscopic loupe and separated for their identification. At the network level we analyzed the potential and real interactions, the degree of connectivity and the degree of nesting. Six species of birds had seeds in their feces, and 90% of the seeds did not exhibit physical damage. The observed seeds were of five native species and five exotic species, and two species were not identified. At the network level, it was observed that the number of potential interactions was 72 and the number of observed interactions was 16, for a connectivity of 22%. The network density was estimated at 0.88 links per species. The degree of nesting of the network was NODF=28.09, with a higher degree of nesting in the birds (NODF=30.3) than in the plants (NODF=18.33). The interaction network made up of birds and bird-dispersed plants from the Espinal forest exhibited low connectivity, in which some birds are generalists and interact with a subset of plant species with fewer interactions.