Linking structure and functionality in mutualistic networks: do core frugivores disperse more seeds than peripheral species?

GOMEZ, MARIA DANIELA; BLENDINGER PEDRO GERARDO; RUGGERA, ROMÁN; MARSHAK, CHARLIE

OIKOS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 125 p. 541 - 555

0030-1299

Seeddispersal networks are often organized in nested structures in a way that a few core species can disproportionally affectthe remaining species in a network, in both the ecological and evolutionary sense. Yet, the relative importance of core andperipheral species has not been properly tested in seed dispersal network studies. We determined core species from 10 localseed dispersal networks composed by fleshy-fruited plants and frugivorous birds. Each of those local quantitative networkswas characterized with a core quality value, a core score for each species and a threshold value between core and peripheralspecies. From a total of 52 bird and 69 plant species that interacted in the study area, only 8 and 15, respectively, wereidentified as core. Each local network had a core that comprised a small number of birds and plants, always lower than30% of the interacting species. There was no difference in the quantitative component of seed dispersal effectiveness (QC)provided by the frugivorous bird assemblage to plant functional groups clustered according to their growth form and fruitcharacteristics. Core birds dispersed seeds from each of these plant functional groups with a higher QC than peripheralspecies. Thus, we empirically demonstrate for the first time that seed dispersal networks at a regional scale have a small coreset of fruit-eating birds, upon which heavily rely most fleshy-fruited plants for their seed removal. Hence, the activity of justa few core frugivores could deeply impact the demography of an entire assemblage of fleshy-fruited plants.