Habitat structure and predator diversity jointly shape the arrangement of predator-prey networks.

Research Highlight: Chen, J., Wang, M. Q., Luo, A., Zhang, F., Chesters, D., Liu, S., Li, Y., von Oheimb, G., Kunz, M., Zhou, Q. S., Bruelheide, H., Liu, X., Ma, K., Schuldt, A., & Zhu, C. D. (2025). Bottom-up and top-down effects combine to drive predator-prey interactions in a forest biodiversity experiment. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70103. Habitat structure influences predator-prey and predator-predator interactions and may interact with predator diversity to determine food-web dynamics. However, only a limited number of studies have investigated how habitat structure and predator diversity jointly shape the predator-prey network. Using molecular analysis of spider gut content, Chen et al. (2025) investigated how various measures of tree diversity and spider phylogenetic diversity shaped the spider-prey network. The spider-prey network was characterized by prey richness, generality, vulnerability and niche overlap in young forest canopies. When considering all spiders together, both tree and spider diversity led to increased prey richness, prey vulnerability and niche overlap, but generality was consistent. However, when spiders were divided into two foraging guilds, web-builders and hunters, the factors driving the food-web structure varied between them. Although both spider diversity and habitat structure affected the spider-prey network, their relative importance differed between the two guilds. For web-builders, phylogenetic diversity was the main driver and high phylogenetic diversity of spiders led to an increase in prey richness, generality, prey vulnerability and niche overlap. For hunting spiders, the tree vertical diversity was an important factor shaping the network structure and higher vertical diversity led to a reduction in prey richness and diet breadth. Overall, the results show that the bottom-up effect of tree diversity and the top-down effect of spider diversity combined to jointly determine the structure of the spider-prey network. However, the impact of tree diversity and phylogenetic diversity of spiders on the structure of the spider-prey network was conditioned by a measure of tree diversity and spider foraging guilds. The results have important implications for forest management, and foresters should aim to maintain heterogeneous forests rather than simple monocultures to enhance predation pressure by spiders on pests and to ensure ecosystem resilience.