Potential ecological suitability of Epimedium sagittatum in China under climate change based on an optimized MaxEnt...

Epimedium sagittatum is an important tonic medicinal plant rich in prenylated flavonoids represented by icariin, and its wild resources are affected by harvesting pressure, habitat change, and climate change. Based on 160 spatially thinned occurrence records from CVH and GBIF and 103 candidate environmental variables, this study used an optimized MaxEnt model to evaluate the current and future potential ecological suitability of E. sagittatum in China. After variable screening, 15 predictors were retained. Kuenm parameter tuning indicated that the optimal model used a regularization multiplier of 3.2 and a feature combination of linear, product, and threshold features. The optimized model had a training AUC of 0.9597 and a test AUC of 0.9475 +/- 0.0095. The cumulative contribution of minimum temperature of the coldest month (bio_6), May solar radiation (srad_05), November precipitation (prec_11), and temperature seasonality (bio_4) was 80.8%. Under current climatic conditions, the total suitable area was 1.38 × 10⁶ km², mainly concentrated in Hunan, Hubei, Jiangxi, Anhui, Zhejiang, and adjacent humid regions. Future projections were adjusted to the 2050s and 2090s and compared under SSP1-2.6, SSP2-4.5, and SSP5-8.5. Total suitable area ranged from 1.37 × 10⁶ to 1.51 × 10⁶ km² in the 2050s and from 1.41 × 10⁶ to 1.43 × 10⁶ km² in the 2090s. Centroids shifted 22-55 km relative to the current centroid, generally toward the north but without a monotonic trajectory. These results provide a spatial reference for resource conservation, field surveys, and cultivation-zoning planning of E. sagittatum.