Forest loss and habitat changes reduce hummingbird functional diversity and the specialization of their interactions with plants in the tropical Andes

Abstract

The expansion of agricultural landscapes is one of the main drivers of biodiversity loss around the world; the environmental gradients resulting from these landscape changes, however, allow an assessment of how biodiversity responds to environmental change. Functional diversity and mutualistic interactions between plants and animals represent an important aspect of biodiversity. In particular, the interactions between hummingbirds and plants stand out for their morphological specialization. Here, we evaluated how changes in landscape attributes affect the functional diversity and hummingbird-plant interaction networks in the coffee-growing region of the Colombian Andes. We described the functional diversity of hummingbirds and their interaction networks with plants in circular plots with a diameter of 50 m located in forests and coffee agroecosystems distributed along a landscape transformation gradient. We found that network specialization in forests is positively related to forest coverage of the landscape, while the relationship with landscape diversity and heterogeneity was weak. In contrast, we found no relationship between landscape variables and network specialization in coffee agroecosystems where the networks are less specialized and less modular compared to forests. A structural equation model (SEM) showed that hummingbird functional diversity had a significant relationship to landscape structure, while the specialization of hummingbird-plant networks was mainly affected by the amount of forest in the landscape. Although no significant direct relationship was found between hummingbird functional diversity and network specialization, SEMs show that, when considering a mediating role of functional diversity, the specialization R2 coefficient increased. Based on our results, we suggest that changes in the diversity and structure of ecological networks were a consequence of the impacts of human intervention on landscapes and natural habitats.