Forest-pasture shifting alters the assemblages of seed-removing ants in southwestern Brazilian Amazon

Abstract

Several studies have evaluated the impacts of intensified human activities on biodiversity, but far less effort has been directed toward evaluating the maintenance of ecosystem functions in human-modified landscapes. We investigated the impacts of habitat shifts from forest to pasture on assemblages of seed-removing ants in the southwestern Brazilian Amazon. We specifically addressed the following hypotheses regarding assemblages of seed-removing ants: (i) pasture ant assemblages have fewer species than do forest ant assemblages and are composed of a markedly different set of species; (ii) pasture ant assemblages remove less seeds than do forest ant assemblages; and (iii) forest and pasture ant assemblages contain different sets of key species for seed removal. We collected ants that were baited with artificial seeds in 10 forest areas and 10 adjacent pastures and found that shifting from forest to pasture reduced the number of species of seed-removing ants and altered species composition. We also found that, although seed removal percentage of was higher in pasture, these species were low quality seed dispersers, which was supported by our identification of key species for seed removal. We conclude that when considering the removal of seeds by ants as a proxy to assess the role of biodiversity in ecosystems, it is necessary to consider the importance of each species for removal according to habitat type affinity.  Our findings highlight the importance of forest habitat for the effective conservation of ant diversity and their ecological functions in human-modified ladscapes.