Cushion plants increase and maintain alpine insect diversity through sustaining plant-insect interaction networks

Alpine cushion plants are well-known facilitators of plant diversity, but their influence on insect communities remains poorly understood, limiting our knowledge of biodiversity maintenance in extreme environments. Using species network theory, we examined how nine coexisting cushion plant species influenced insect diversity and community dynamics in the Himalaya-Hengduan Mountains across three consecutive years with varying seasonal conditions. Our findings demonstrated that cushion plants consistently supported significantly higher insect diversity and abundance than non-cushion plants, maintaining 3.5-4.2 times more species and 4.5-8.8 times more individuals. By hosting 7-46 exclusive insect species per season, cushion plants enhanced community-wide insect richness by 25.93-112.20% and abundance by 2.31-41.64%. Network analyses revealed that cushion plants occupied more central positions (higher closeness and betweenness centrality) and often acted as module hubs or connectors, whereas non-cushion plants were mostly peripheral. These structural roles were strongest in 2022–2023 but weakened in 2024. Extinction simulations showed that insect persistence declined most rapidly when cushion plants were removed first, underscoring their ecological importance. Our findings identify cushion plants as keystone species in alpine plant–insect interaction networks and highlight their role in supporting insect diversity through complex interaction networks. Although climate change may reduce some environmental stress, many alpine insects are likely to remain dependent on cushion plants’ microhabitat provisioning. Consequently, their climate-sensitive decline could jeopardize alpine insect biodiversity, emphasizing the need for their conservation.