Hydrodynamics rather than water temperature shapes the macroinvertebrate communities in alpine rivers on the Qinghai–Xizang Plateau

Climate change is rapidly altering global glacier-fed rivers, with prevailing models assuming that water temperature increases dictate aquatic community succession. However, this thermal-centric paradigm struggles to explain biodiversity patterns within the extreme topographic and hydrologic gradients of the Third Pole. By analyzing macroinvertebrate assemblages across the Yarlung Tsangpo Basin, we show that hydrodynamic condition, rather than water temperature, primarily influences biodiversity and community assembly in these high-altitude alpine rivers. With hydrodynamic intensity indicated by specific stream power, taxa richness exhibits a universal unimodal response, consistently peaking under moderate hydrodynamic intensity (1 to 10 W m⁻²). Extreme stream power acts as a severe physical filter, driving a stark taxonomic shift from filamentous-gilled species in moderate flows to robust, flat-bodied specialists capable of resisting ultra-high-power environments. These findings demonstrate that localized hydrodynamic modulation—rather than unattainable temperature control—provides a highly viable, climate-resilient strategy to safeguard biodiversity in the Third Pole and analogous alpine river networks worldwide.