Modeling global ecological niche shifts of Osyris spp. under climate change scenarios: conservation priorities for a threatened genus

The genus Osyris L. comprises ecologically and economically important evergreen shrubs or small trees, with particular African species currently threatened by unsustainable exploitation. This study projected potential ecological niche shifts for Osyris under four Shared Socioeconomic Pathways (SSPs) using digitized herbarium specimen localities and 20 environmental variables. The genus currently occupies a broad range between 41.32°N–34.85°S latitude and 9.27°W–109.03°E longitude, at elevations from 0 to 3900 m. High-suitability areas cluster primarily in the European-Mediterranean region, eastern/southern Africa, western South America, and Southeast Asia. Projections indicate a significant decline in high-suitability area under all SSP scenarios (SSP126, SSP245, SSP370, SSP585) compared with current conditions. Jackknife tests identified Bio11 (mean temperature of coldest quarter, 41.5%), Bio12 (annual precipitation, 26.5%), Bio3 (isothermality, 10.7%), and Bio7 (temperature annual range, 9.0%) as the dominant bioclimatic constraints. Crucially, temperature-related factors (Bio11, Bio3, and Bio7; 61.2%) were pivotal determinants, with projections indicating a decline in both the overall highly suitable area for Osyris and the potentially suitable area for O. lanceolata, suggesting that some species within the genus may face severe habitat shrinkage. These findings underscore the urgent need to prioritize in situ conservation within stable refugia and implement adaptive management strategies to mitigate climate-induced habitat degradation across the genus.