Future of high mountain endemic species under climate change: predicting the potential scenarios for Stellaria pulvinata in the Altai Mountains

Mountain ecosystems are vulnerable to climate change and unsustainable human activities worldwide, as evidenced by shifts in vegetation and losses of plant species diversity and habitats. These phenomena have a particularly important effect on narrow endemics that are sensitive to environmental and climatic changes. In the Altai Mountain Country (AMC), the endemic plant species Stellaria pulvinata Grubov (Caryophyllaceae) is found in small geographic areas at high elevations between 2,070 and 4,000 m. However, its current geographic range is shrinking owing to global warming, climate change, and habitat loss. Here, we aimed to assess the habitat suitability of S. pulvinata using MaxEnt to identify key environmental factors and predict shifts in its distribution under different climate scenarios (SSP2-4.5 and SSP5-8.5) for the 2050s and 2090s. We tested five algorithms using the "sdm" package in R, and found that the MaxEnt algorithm demonstrated the highest predictive performance (area under the curve (AUC) = 0.96, true skill statistic (TSS) = 0.89, correlation coefficient (COR) = 0.24, deviance = 0.23); therefore, MaxEnt was selected for subsequent analyses. Currently, the total potentially suitable habitat area for S. pulvinata spans approximately 169,659 km² and covers 25.86% of the AMC. We predicted that the total suitable habitat area for S. pulvinata will decline to 20.59% by the 2050s and 19.19% by the 2090s under the SSP2-4.5 future climate scenario, with the center of suitable habitats shifting southeast. MaxEnt analysis identified elevation, temperature (Bio 4), and precipitation seasonality (Bio 15) as the most significant factors influencing its distribution. This species is expected to shift to higher elevations under future climate conditions (SSP2-4.5) by 2050 and 2090, leading to further range contraction. Notably, only 31.73% of the current range falls within protected areas, thus highlighting a substantial conservation gap. To conserve S. pulvinata, it is important to adopt in-situ and ex-situ conservation measures, conserve germplasm resources through seed banking and tissue culture, and implement strict management policies to minimize human disturbance and promote natural regeneration. These findings highlight the need for targeted conservation measures to address the ongoing threats to this species.