Species richness and network topology patterns in Neotropical plant-galling communities changes along an urbanization gradient

The conversion and fragmentation of natural environments in urban areas can have major consequences on species diversity and ecological interactions. Plant-insect interactions may be dramatically altered because many plants and insect species are unable to tolerate the biotic and abiotic changes associated to urban ecosystems. In the present study, we tested if the network structure between host plants and galling insects changes along urban, peri-urban and rural areas. Our study was performed in nine areas of Cerrado sensu stricto (Neotropical savanna) along an urbanization gradient in the municipality of Montes Claros, Brazil. In total, we sampled 100 galling insect morphospecies and 54 host plant species. Our results show a negative effect of urbanization on the species richness of host plants and galling insects. Furthermore, urbanization increases connectance and reduces the modularity of plant-galling networks. Our findings indicate that the plant-galling communities become poorer and less specialized as they approach more urbanized environments. In this way, our results show that the plant-herbivore communities tend to be functionally depauperate as Cerrado environments are disturbed.Implications for insect conservationOur results show that urbanization has negative effects on insect conservation, resulting in less diverse and specialized plant-galling networks in urban environments. This suggests that plant-herbivore communities can be taxonomically and functionally impoverished in urbanized habitats.