Distribution response of the diploid hybrid species Hippophae goniocarpa to climate change based on a three-dimensional geographic gradient.

Hippophae goniocarpa has been confirmed by molecular ecological evidence as a diploid hybrid species derived from the natural hybridization of Hippophae rhamnoides subsp. sinensis and Hippophae neurocarpa. Its distribution is strictly confined to sympatric hybrid zones of its parental species, exhibiting neither niche expansion nor significant heterosis. While existing studies have largely focused on the genetic evidence and mechanisms underlying its hybrid origin, the response of its geographic distribution to climate change remains largely unknown. To predict the distribution patterns and dynamics of the endemic Chinese hybrid H. goniocarpa under current and future climate scenarios, and to identify critical refugia for its long-term persistence, this study integrated species occurrence records of both parental species with multidimensional environmental variables, including climate, soil, topography, and human activity. Using an R-optimized MaxEnt modeling framework, we simulated the potential suitable habitats of each parental species under current conditions and across three future time periods under three Shared Socioeconomic Pathways. The potential distribution range of H. goniocarpa was subsequently delineated via overlay analysis as the intersection of the projected suitable habitats of its two parental species. Spatiotemporal dynamics and elevational response patterns were systematically analyzed. The models exhibited excellent predictive performance, with mean AUC values of 0.943 and 0.927 and TSS values of 0.892 and 0.867 for H. rhamnoides subsp. sinensis and H. neurocarpa, respectively. The current maximum potential suitable habitat area of H. goniocarpa is 47.52 × 104 km2, with core areas concentrated in the eastern margin of the Qinghai‑Tibet Plateau and the western Loess Plateau. Centroid trajectory analysis identifies the current centroid at 99.16°E, 33.35°N. Under future scenarios, distinct migration trajectories emerge across emission pathways. Under the medium emission scenario (SSP370), the centroid exhibits a slow northeastward trend, whereas under extreme emission scenarios (SSP126 and SSP585), it shifts predominantly southeastward or southwestward, with SSP585 showing the greatest migration distances. Notably, in contrast to the prevailing pattern of significant upward elevational migration observed in many species, the core elevational range of H. goniocarpa remains largely stable over the next eight decades, with no pronounced upward shift detected. The stable areas identified in central and western China serve as critical climatic refugia for H. goniocarpa and warrant priority consideration in future conservation planning. These findings provide a scientific basis for biodiversity conservation in the Helan Mountains and surrounding regions.