Present and Future Climatic Suitability of Castilleja tenuiflora in Mexico

Climate change can reshape the climatic conditions available to mountain plants. Using MaxEnt, we modelled the current and future climatic suitability of Castilleja tenuiflora Benth., a medicinal hemiparasitic plant, across Mexico and quantified its spatial overlap with Mexican Protected Natural Areas (PNAs). The final model (LQ, RM = 0.5), calibrated with 194 spatially filtered presence records and seven bioclimatic predictors, achieved a mean spatial-validation AUC of 0.794 ± 0.093. Annual mean temperature and temperature seasonality were the dominant predictors, jointly accounting for approximately 96% of model contribution. Current climatic suitability above the 10th-percentile training-presence threshold (P10 = 0.162865) covered approximately 548,819 km2. Future projections using CMCC-ESM2 under SSP1-2.6 and SSP5-8.5 for three periods spanning 2021–2080 showed net contractions in climatically suitable area under all scenarios. By 2061–2080, the area above P10 decreased by 41.6% under SSP1-2.6 and by 65.3% under SSP5-8.5. Across all projections, losses of climatically suitable area substantially exceeded gains, while the area maintaining suitable conditions decreased towards the end of the century; proportionally greater contractions were observed at more restrictive suitability thresholds. Currently, approximately 48,690 km2 of ≥P10 climatic suitability overlaps the PNA network, decreasing to 23,638 km2 under SSP5-8.5 by 2061–2080. Nevado de Toluca, Iztaccíhuatl-Popocatépetl, and Pico de Orizaba consistently retained areas above the P90 suitability threshold under current conditions and all six future projections. These results indicate a substantial potential contraction of climatic suitability for C. tenuiflora and highlight protected areas retaining suitable climatic conditions as priorities for field verification, monitoring, and conservation planning.