Seasonality and extrafloral nectaries shape plant–spider networks

Abstract

Extrafloral nectaries (EFNs) are key plant traits mediating multitrophic interactions, yettheir role in structuring plant–spider communities at the network level remains poorlyunderstood. Here, we provide the first empirical network analysis of plant–spider interactionsin the Brazilian Cerrado, evaluating how EFNs and climatic seasonality shape interactionarchitecture and community composition. From October 2020 to September 2021, wequantified spider occurrences on flowering plants with and without EFNs across dry and rainyseasons and constructed quantitative bipartite interaction networks. We analyzed connectance,nestedness, modularity, and specialization, comparing observed values against null modelexpectations. Plant–spider networks exhibited highly non-random structures, with EFN-bearingplants promoting lower specialization and significant modularity across seasons. Contrary toexpectations, connectance was higher during the dry season, while null models revealed thatbiological constraints limited interaction realization even under high resource availability.Seasonal shifts strongly altered network topology but did not affect spider species composition,which remained stable across plant types and seasons. Our results indicate that EFNs act asstructural hubs that reorganize interaction patterns without driving species turnover,highlighting the importance of facultative interactions and behavioral flexibility in maintainingcommunity stability in seasonal savanna ecosystems.