Standardized diversity estimation uncovers global distribution patterns and drivers of stream insects.

Freshwater insect biodiversity is under global threat from anthropogenic stressors, yet the roles of natural and anthropogenic drivers remain unclear. Here, we examine 783 river basins to map the global diversity and explore the effects of sampling bias, natural, and anthropogenic factors on four major taxa: Ephemeroptera, Plecoptera, Trichoptera and Odonata (EPTO). About 62% of basins were under-sampled, especially in the Global South. Standardized diversity metrics (especially Shannon- and Simpson-based) better captured global diversity patterns of insect than observed diversity. Standardized taxonomic and functional diversity showed two latitudinal peaks, with a minor peak at the equator and a higher peak at ~40°N. Landscape factors had the highest relative impact on taxonomic diversity, while both climatic and landscape factors were primary drivers of functional diversity. By controlling for sampling biases, we provide more accurate insights into the drivers of freshwater insect diversity to inform effective stream conservation and management.