Plant-herbivore networks composed by adult and immature insects have distinct responses to habitat modification in Brazilian savannas

Human-induced habitat modification can affect species interactions and ecological networks composed of specialized species may be more susceptible to these effects. Immature and adult insect herbivores have different mobility and specificity levels related to their host plants, which can affect their tolerance to anthropic disturbances. In the present study, we compared the structure of plant-herbivore networks composed of adult and immature insects in 16 Neotropical savanna sites under different land-use intensification levels. We compared insect species richness, insect abundance, connectance, specialization, generality, vulnerability, modularity, and nestedness in plant-immature insect and plant-adult insect networks occurring in preserved and non-preserved areas. In total we sampled 328 individuals of 98 species of host plants and 557 individuals of 310 species of insect herbivores (275 individuals of 143 species of immature insects and 479 individuals of 196 species of adult insects). Although the richness of insect species did not differ between the networks, plant-immature insect networks had a lower insect abundance, generality and nestedness than networks of adult insects. On the other hand, connectance was lower for networks of adults than for networks of immature insects. Our results also show that the effects of habitat modification are more pronounced for immature insects than for adults, as network connectance increases and network vulnerability decreases between preserved habitats and disturbed habitats. Our findings support previous warnings that habitat modification can alter plant–herbivore interactions, and advance the understanding of how these effects can be different for assemblages composed of adult and immature insects. Our results indicate more consistent effects of habitat modification on immature insect interactions, which showed more specialized networks in preserved environments. Thus, our results contribute to the understanding of how plant-insect interactions are structured in highly disturbed environments, such as Neotropical savannas.