Extrafloral nectaries influence Lepidopteran herbivore communities and network structure in the Brazilian Cerrado.

Abstract

Background and aims: Extrafloral nectaries (EFNs) are plant glands that secrete nectar, attracting ants and other predatory arthropods and mediating multitrophic interactions. EFNs provide indirect defence by reducing herbivory, often enhancing plant growth, survival, and reproduction. Their effects on herbivore communities are complex, as some species can evade ant predation, altering abundance, diversity, and composition. EFNs can shape network-level interactions, including modularity, nestedness, and specialization. However, few studies have assessed their simultaneous effects on community structure and network properties, limiting understanding of their broader ecological roles.

Methods: To address this gap, here we investigated whether EFNs influence Lepidopteran communities and network structure, hypothesizing that EFN-bearing plants would support higher diversity, host distinct assemblages, and exhibit greater modularity by acting as ecological filters. We examined 56 plant species in the Brazilian Cerrado (30 with EFNs, 26 without) over two years, measuring Lepidopteran abundance, diversity, community composition, and network properties, including specialization, plant centrality, modularity, nestedness, and interaction turnover.

Key results: Our results showed that EFN-bearing plants exhibited higher Lepidopteran abundance and diversity and harboured distinct Lepidopteran assemblages compared to non-EFN plants. At the individual network level, EFNs enhanced plant centrality, acting as connecting hubs of interaction. At the structural network level, EFNs increased modularity, whereas nestedness and Lepidopteran specialization remained unchanged. Species interaction turnover also differed between EFN and non-EFN plant species, highlighting the role of EFNs in structuring community dynamics.

Conclusions: By jointly analysing abundance, diversity, and network architecture, this study provides a comprehensive assessment of how EFNs influence multitrophic interactions.