Tritrophic Interactions and Parasitoid Community Structure of Gall-Inducing Herbivores in Arid Desert Ecosystems of Northern Xinjiang, China

Tritrophic interactions among plants, gall-inducing herbivores, and their parasitoids are critical components of arid desert ecosystems, yet their complex network structures, and evolutionary adaptations remain poorly understood. This study elucidates the ecological networks and life-history strategies of three distinct gall inducers and their associated parasitoid communities on Lycium ruthenicum, a keystone shrub in Northern Xinjiang, China. First, we report the globally novel gall-inducing behavior in the genus Scrobipalpa, identifying Scrobipalpa erichiodes (Lepidoptera: Gelechiidae) as the inducer of swollen twig galls, where gall morphology acts as a significant predictor of internal larval development. Alongside S. erichiodes, we characterized the phenological dynamics of Aceria pallida (leaf galls) and Contarinia sp. (flower bud galls). Furthermore, we recovered a highly complex parasitoid community comprising 13 species, establishing multiple new host records. The dominant parasitoids regulating these gall inducers were Pholetesor teresitergum, Cirrospilus pictus, and Pseudotorymus jaapiellae, respectively. Notably, the high dominance of C. pictus on the gall mite A. pallida represents an unusual cross-guild host shift, highlighting the adaptive plasticity of natural enemies in resource-heterogeneous desert environments. Finally, laboratory assays revealed a significant negative correlation between increasing temperatures (15°C-30°C) and the adult longevity of these dominant parasitoids. These findings not only provide novel insights into the evolutionary ecology of gall-induction but also underscore the vulnerability of parasitoid-mediated top-down control to thermal stress. Ultimately, this research deciphers the complex tritrophic networks sustaining arid ecosystems, offering a theoretical foundation for predicting species interactions and community stability under changing climate conditions.