Climate-Driven Range Dynamics of the High-Altitude Frog Nanorana parkeri in Xizang, China: A Bias-Corrected,...

The climate sensitivity of high-altitude amphibians on the Qinghai-Tibet Plateau remains poorly quantified. We assessed habitat suitability for the plateau-endemic frog Nanorana parkeri across Xizang, China. Using 52 thinned occurrence records and nine predictors (spanning climate, terrain, and hydrological accessibility), we built a bias-corrected random forest (RF) model with VIF-screened variables, constrained complexity, and out-of-fold (OOF) evaluation, including spatial-block cross-validation. Gradient boosting (GBM) and a regularized GLM were fitted on identical data, and the RF was projected onto a two-GCM CMIP6 ensemble under four Shared Socioeconomic Pathways through 2100. The RF achieved OOF and spatial-block AUCs of 0.750 and 0.672 (GLM 0.734/0.691; GBM 0.692/0.584); all three converged on a current suitable area of 8.13 × 10⁵ km². Under future climate, net habitat expansion reached 117-126% of current area by 2081-2100. Range turnover was asymmetric: ~96% remained stable, 3-5% was lost, and 17-29% was gained upslope. Inter-GCM uncertainty was low (SD 0.016-0.022), but MESS extrapolation was substantial (55-67% of Xizang). Net upslope expansion represents a robust climatic opportunity, but realised gains depend on persistent breeding waters. Conservation actions should prioritise protecting stable core breeding waters in Southern and Southeastern Xizang and monitoring upslope colonisation fronts.