Disentangling the mechanisms behind indirect interactions between plants via shared pollinators: Effects of neutral and niche‐based processes

Abstract Indirect interactions between plants via shared pollinators play a crucial role in structuring and stabilizing ecological communities. Although both neutral (interactions occurring in proportion to species abundance) and niche‐based (involving morphological matching and phenological overlap) processes are known to structure plant–pollinator interactions, how these processes drive the formation and maintenance of indirect interactions between plants in pollination networks remains poorly understood. Here, we investigated a species‐rich alpine meadow in southwest China to disentangle the potential mechanisms underlying indirect interactions between plants via shared pollinators. We analysed data from the plant–Hymenoptera network, the plant–Diptera network and the whole network combining all plants and pollinators to (1) quantify the prevalence of indirect interactions between plants and their contribution to network structure; (2) assess how plant traits related to neutral (flower abundance) and niche‐based (flower phenology, morphology and phylogeny) processes influence indirect interactions between plants; (3) evaluate the extent to which indirect interactions between plants could be predicted by neutral and niche‐based processes. We found that indirect interactions between plants were highly prevalent across all networks and were related to increased contribution to nestedness, an important structure for network stability and the maintenance of species diversity. Corolla‐tube length dissimilarity was the primary driver of the probability of indirect interactions between plants in both the whole network and the plant–Hymenoptera network, while flowering length had the greatest influence in the plant–Diptera network. Across all networks, flower abundance emerged as the key factor determining the strength of these interactions. Moreover, neutral and niche‐based processes effectively predicted indirect interactions between plants, with neutral processes showing stronger predictive performance than the others. Synthesis . Overall, our study quantifies the prevalence of indirect interactions between plants in pollination networks and their influence on network structure and systematically elucidates the potential mechanisms underlying these interactions. These findings offer new insights into the ecological processes that govern species coexistence and contribute to the maintenance of biodiversity in plant–pollinator communities.