Defaunation Leads to Functional Loss in a Tropical Biodiversity Hotspot

Abstract

Defaunation is considered one of the main drivers of modifications in tropical ecosystems, extirpating many large-sized vertebrates, which in turn compromises key ecological functions. Although much attention has been given to predict the effects of species loss on ecological processes, there is a lack of information on the large-scale effects of defaunation. Knowledge gaps such as at which spatial scales biodiversity loss affects ecosystem functioning and ecological functions, and what is the relationship between species loss and preservation of ecological functions, remain poorly understood. Mammals perform important ecological functions, but are widely affected by habitat loss and modification, being considered as priority for conservation worldwide. Thus, determining the impact of land use changes on ecological patterns and process performed or influenced by mammals is of critical importance. Here, we detected erosion in the prevalence of ecological functions performed by mammals mediated by changes in the landscape structure of a tropical biodiversity hotspot in Brazil. By analyzing the loss of different ecological functions (vertebrate and invertebrate predation, seed dispersal, seed depredation, herbivory) in a defaunation gradient, we observed that vulnerable functions (performed by sensitive species) were positively related to patch size and forest cover and negatively related to anthropogenic cover. These relationships were reversed for persistent functions (performed by resilient species). Vulnerable functions were virtually restricted to large forest remnants, while persistent functions were prevalent in human-modified landscapes. Our study adds knowledge on how large-scale defaunation mediated by changes in landscape structure affects ecological functions.