Plant richness and vegetation structure drive the topology of plant-herbivore networks in Neotropical savannas

Abstract

Plants and phytophagous insects make up the highest terrestrial diversity on the planet, forming complex interspecific interaction networks. Interaction networks are an important tool to understand how ecological interactions shape plant-herbivore assemblages. In the present study, we tested the hypotheses that the plant species richness and vegetation structure (vegetation cover and vegetation height) (i) drive the richness and abundance of herbivorous insects and (ii) determines topological patterns (connectance, specialization and modularity) of plant-herbivore networks. We sampled ten different areas in the Neotropical savannas to assess those hypotheses and constructed plant-herbivore interaction matrices using species composition data. Plant-herbivore interaction networks comprised 298 plants of 60 species, 421 insects distributed in 96 morphospecies, and totalizing 218 interactions. We found that plant species richness positively influenced the species richness of herbivorous insects, whereas average vegetation height negatively affected the species richness of herbivorous insects. The abundance of herbivorous insects was negatively affected by plant species richness, and by vegetation height. Species richness and structure of plant communities also significantly affected network topological parameters. Network connectance was negatively influenced by plant richness and positively affected by vegetation cover. Besides, plant species richness positively influenced network modularity, whereas vegetation height negatively affected network modularity. However, the plant community diversity and vegetation structure did not affect network specialization. Our results show that both plant community diversity and vegetation structure in Neotropical savannas drive the structure of plant-herbivore interaction networks. Considering the current high rates of removal of native vegetation in Brazilian savannas, our findings indicate that the preserving this ecosystem is crucial for maintaining ecosystem services through plant-herbivore interaction networks.