Abstract: The insect gall ecosystem exhibits complex ecological interactions, harbors rich biodiversity, and holds significant agricultural and economic importance. However, insufficient understanding regarding gall complexity, formation mechanisms, and diversification significantly hinders the effective control of gall-inducing pests and the large-scale application of valuable galls. This review discusses the multi-dimensional regulatory mechanisms underlying gall complexity, formation, and diversification, and proposes potential research directions. Galls constitute complex ecological interaction networks centered on insect-plant interactions, in which both biotic and abiotic factors collectively influence the interaction dynamics and phenotypic complexity of galls. Nevertheless, the ecological consequences of these intricate interactions still await systematic elucidation. The complexity of gall-formation mechanisms may explain the overall complexity and phenotypic diversity of galls. Current research implicates that multiple factors are involved in gall formation and diversification, including gene expression changes, effector protein interactions, hormone dynamics, secondary metabolite metabolism, plant physiological shifts, epigenetic modifications, and insect symbionts. However, the detailed mechanisms and synergistic pathways involving multiple factors remain unclear. Future research could integrate multi-omics, artificial intelligence, real-time visualization sensors, and gene editing technologies to advance the following areas: 1) Establish a gall diversity database and develop more model systems similar to Ab‑GALFA; 2) Identify additional insect effector proteins and their target proteins to elucidate their interaction patterns; 3) Clarify the spatiotemporal dialogue mechanisms within hormone regulatory networks (of both insect and plant origin); 4) Elucidate the role of secondary metabolite-mediated insect–plant defense/counter-defense interactions in gall formation and strengthen research on insect detoxification mechanisms targeting gall secondary metabolites. 5) Investigate the roles of epigenetic regulation and insect symbionts in the induction and development of galls; 6) Uncover the synergistic effects and underlying mechanisms of multiple factors in gall formation and diversification. Advances in these fields will elucidate the regulatory mechanisms governing gall ecosystem formation, maintenance, and diversification, thereby providing a theoretical foundation for developing efficient pest control strategies and enabling the large-scale utilization of economically valuable galls.

Key words: insect-plant interaction, ecosystem engineering, defense/counter-defense, gall diversity, gall-inducing insects, insect effectors