Abstract: Alcimandra cathcartii is a Class II nationally protected plant species in China, facing severe threats from climate change. In this study, we predicted changes in its suitable habitat across China under current conditions and four future periods (2030s, 2050s, 2070s, and 2090s) across three climate scenarios (SSP126, SSP245, and SSP585), by combining an optimized MaxEnt model with multivariate environmental similarity surface (MESS) and most dissimilar variable (MoD) analyses. Results indicated reliable model predictions (area under the receiver operating characteristic curve AUC >0.97, true skill statistic TSS >0.93, continuous Boyce index CBI >0.94). Temperature seasonality, precipitation in the hottest quarter, isothermality, precipitation in the coldest quarter, elevation, and mean temperature in the hottest quarter were identified as the key environmental factors influencing the geographical distribution of this species. The current total area of suitable habitat was 76.62×10⁴ km², accounting for 7.98% of total land area in China, with highly suitable habitat (13.01×10⁴ km²) being concentrated in southwestern to southeastern Yunnan and southern Tibet. Under future climate scenarios, the suitable habitat area showed an overall trend of first increase followed by a gradual slowdown. Under the SSP126 scenario, the highly suitable habitat peaked at 35.50×10⁴ km² in the 2070s before contracting. Under the SSP245 scenario, the overall suitable habitat (lowly, moderately, and highly suitable habitats) remained relatively stable. However, under the high-emission scenario (SSP585), degradation risks were most pronounced. The highly suitable habitat sharply declined to 24.58×10⁴ km² in the 2070s. Although it partially recovered by the 2090s, habitat fragmentation in the core areas continued to intensify. Climate anomaly zones expanded overall with increasing emission intensity. The dominant anomaly factors gradually shifted from precipitation-related factors to temperature factors, with the vulnerability of southern concentrated suitable habitats and southeastern marginal areas significantly increasing. Centroid migration analysis showed that the centroids under the SSP126 and SSP245 scenarios migrated overall toward the northeast compared to the current period, while under the SSP585 scenario the migration direction shifted successively compared to the preceding period during the later periods (2050s-2090s), toward the southwest in the 2050s, toward the northwest in the 2070s, and toward the south in the 2090s, reflecting the high instability of suitable habitats under high-emission scenarios. The Yunnan-southern Tibet region is recommended as a priority core conservation area.

Key words: Alcimandra cathcartii, potential suitable habitat, MaxEnt