Human-induced habitat modification affects the structure of insect communities and the topology of plant-herbivore networks in Brazilian Neotropical savannas

Abstract

Human-induced habitat modification can alter various aspects of biological diversity, such as interspecific interactions that form ecological networks. In this study, we investigated how species diversity and the interaction structure of plant-herbivore networks differs between wild, rural and urban fragments of Brazilian savannas. We tested the hypothesis that habitat modification leads to a proportionally greater loss of specialized species and interactions, reducing the diversity of herbivorous insect species, increasing network connectance, and decreasing network modularity. The study was conducted in 2018 and 2019 across 16 savanna fragments located in the Neotropical savannas of Brazil, spanning a gradient of habitat disturbance including wild, rural, and urban areas. In total, we sampled 312 insect species, 94 plant species, and 503 interspecific interactions in 16 plant-herbivore networks. Using a model selection procedure, we found that the conservation status of savanna (wild, rural and urban fragments) was present in all the best-selected models. Our results show that urban and rural areas had a lower proportion of host plants with herbivores, lower insect abundance, and lower richness of herbivorous insects compared to wild areas. In addition to changes in species richness, we also observed that urban areas exhibited more connected, more robust and less modular networks compared to wild areas, supporting our expectations. These findings indicate that the intensification of human-induced habitat modification along the urbanization gradient leads to species loss and generalization of plant-herbivore networks in Neotropical savannas.