Geographic distribution and impacts of climate change on the suitable habitats of two alpine Rhododendron in Southwest China

Mountains of Southwest China (MSC) serve as a prominent geographical distribution center for Rhododendron delavayi and Rhododendron irroratum (Ericaceae). These mountains are currently experiencing an unparalleled warming trend, which poses severe challenges to the survival of these keystone alpine Rhododendron species. However, the geographical distribution responses of these species to climate change remain incompletely understood and are often overlooked. Herein, we constructed ensemble models (EMs) using 10 models of five algorithms to calibrate ecological niche models and predict suitable habitat areas for the two Rhododendron species across four climate emission scenarios over three distinct periods. Our analysis indicated the higher importance of elevation than temperature and precipitation in shaping the spatial distribution of the two alpine Rhododendron species. The current suitable habitats of R. delavayi and R. irroratum have areas spanning 14.85 × 104 and 11.01 × 104 km2, respectively, which are mostly distributed in the western and central regions of MSC. The suitable habitat of R. delavayi is projected to decrease by 15.09% to 75.31%, but the potential habitat of R. irroratum is expected to shrink by12.71% to 76.8% in different future climate scenarios. The suitable habitats of these species may become confined in a "summit trap" within relatively low-altitude regions, whereas habitats distributed at high altitudes may serve as "biological refuges." The future distribution of the two alpine Rhododendron species will shift to high altitudes in westward and northward regions, with substantial thermal and hydrothermal changes as the primary drivers of habitat alteration and migration patterns. The losses or benefits for species under climate warming depend on their ecological niches and geographical location, which provide a geographical guidance for the long-term conservation and sustainable use of species and essential insights into the spatial conservation assessment of alpine plant groups in biodiversity hotspots in the future.