Plant functional and phylogenetic diversity affect herbivorous diversity, but do not alter the structure of plant-herbivore networks

Abstract

Functional and phylogenetic diversity of plant communities can influence the diversity of herbivorous insects and, consequently, the structure of plant-herbivore interactions. However, few studies have evaluated how functional and phylogenetic diversity affect the structure of ecological networks, especially in savanna ecosystems. We investigated whether the functional and phylogenetic diversity of plant communities influenced the topology of plant-herbivore networks in Neotropical savannas. Our study was performed in 12 remnant areas of neotropical savannas in Brazil. We tested the hypothesis that higher functional and phylogenetic diversity in plant communities increases the species richness and abundance of herbivorous insects. Plant communities with higher functional and phylogenetic diversity should be expected to exhibit more specialized and modular plant–herbivore networks. Here, we sampled 255 insect species, 73 plant species, and identified 218 distinct plant-herbivore interactions. Plant functional diversity reduced the richness and abundance of herbivorous insects, and leaf thickness was the only plant trait associated with increased herbivore richness and abundance. Furthermore, we found that phylogenetic diversity increased the insect species richness, supporting our hypotheses. However, contrary to our expectations, our results show that neither the functional nor the phylogenetic diversity of plant communities affected the topological descriptors of plant-herbivore networks. This study suggests that, while plant functional and phylogenetic diversity shapes the diversity of herbivore communities, its impact on network structure may be mediated by additional ecological or environmental factors, such as habitat structure, resource availability, and microclimatic variation.