Effects of increasing aridity and chronic anthropogenic disturbance on seed dispersal by ants in Brazilian Caatinga

1. Anthropogenic disturbance and climate change are the main drivers of biodiversity loss and ecological services around the globe. There is concern that climate change will exacerbate the impacts of disturbance and thereby promote biotic homogenization, but its consequences for ecological services are unknown. 2. We investigated the individual and interactive effects of increasing chronic anthropogenic disturbance (CAD) and aridity on seed dispersal services provided by ants in Caatinga vegetation of northeastern Brazil. 3. The study was conducted in Catimbau National Park, Pernambuco, Brazil. Within an area of 214 km2, we established nineteen 50 x 20 m plots that encompassed gradients of both CAD and aridity. We offered diaspores of six plant species, three myrmecochorous diaspores and three fleshy fruits that are secondarily dispersed by ants. We then quantified the number of interactions, seed removal rate and dispersal distances, and noted the identities of interacting ant species....