Urbanization and climatic factors drive insect diversity along climatic gradients at urban green spaces in eastern China

Urban green spaces (UGS) are vital habitats for maintaining insect diversity within cities. However, the key factors driving insect biodiversity under accelerating urbanization remain poorly understood. This study systematically investigates insect diversity and its environmental drivers across 200 sampling sites distributed along an urban-to-rural gradient in 4 climatically distinct cities of China: Changchun, Beijing, Hangzhou, and Haikou. We identified 102 common insect species across 8 orders, with Diptera dominating overall abundance. Species richness was highest in farmland and well-managed urban parks, while roadside and residential habitats exhibited reduced or variable diversity. Insect abundance and composition showed significant spatial variation, strongly influenced by UGS type and urbanization intensity. Diptera emerged as key indicator taxa, responding sensitively to urbanization gradients. A generalized linear mixed-effects model framework was developed to integrate large-scale urban environmental variables with local habitat characteristics, enabling a comprehensive assessment of how urbanization and climate combinedly influence insect diversity across cities. Principal coordinate analysis and non-metric multidimensional scaling revealed that both land use and climate zone contributed to community differentiation, with the strongest effects observed in transitional habitats. Mantel tests and random forest models demonstrated that the key environmental drivers of diversity were taxon- and city-specific, including geographic location, particulate matter, wind speed, and floral diversity. Maximum ecological niche model analysis revealed divergent trends in future habitat suitability, driven by distinct climatic variables in each city. Overall, our findings underscore the importance of region-specific conservation strategies in sustaining insect diversity in urban ecosystems.