Bat-fruit networks structure resist habitat modification but species roles change in the most transformed habitats

Abstract

Species do not function as isolated entities, rather they are organized in complex networks of interactions. These networks develop the ecological processes that provide ecosystem services for human societies. Understanding the causes and consequences of changes in ecological networks due to landscape modification would allow us to understand the consequences of ecological processes. However, there is still theoretical controversy and few empirical data on the effects of network characteristics on the loss of natural environments. We investigate how bat-fruit networks respond to three landscapes representing the gradient of modification from pre-montane forest to a heterogeneous agricultural landscape in the Colombian Andes (continuous forests, forest fragments, and crops). We found that forest contained smaller bat-fruit networks than forest fragments and crops. Modified landscapes had similar ecological network structures to forest (nestedness and modularity), but crops contained less specialized networks compared to forests and fragments and the species role in these habitats change. The networks in the rural coffee landscape maintain their structure in the different transformation scenarios, indicating that seed dispersal services are maintained even in the most transformed scenarios. This could be related to the high heterogeneity present in this rural landscape. Although the number of species does not decrease due to transformations, species change their roles in the most transformed habitats. This result sheds light on the way that biodiversity responds to anthropogenic transformations, showing higher stability than theoretically predicted.