Comparative Species Distribution Modeling of Two Rare Hedysarum Species in European Russia Under Current and Future Climate Scenarios

This study aimed to identify the main environmental drivers of the potential ranges of the rare species Hedysarum grandiflorum and Hedysarum argyrophyllum, to compare their ecological responses, and to assess changes in habitat suitability under current and projected climate conditions. The modeling program MaxEnt was used, with predictors including climate variables from CHELSA Bioclim, a digital elevation model, and variables from the SoilGrids global digital soil mapping system. The results indicate that climatic and orographic variables play a key role in determining the potential ranges of both species. The distribution of H. grandiflorum is more strongly influenced by soil properties, notably cation exchange capacity, whereas H. argyrophyllum is associated with nutrient-poor substrates. Model projections under the RCP4.5 and RCP8.5 climate scenarios suggest a potential local increase in modeled habitat suitability during 2040–2060, followed by a decline in highly suitable areas during 2060–2080, particularly for H. argyrophyllum. Although the models do not project complete extinction or a uniform large-scale reduction in the total potential range for either species, they indicate substantial regional declines in habitat suitability and marked reductions in the number of highly suitable habitats under the future climate scenarios considered. Model outputs can help identify areas of high and stable suitability that may serve as priorities for the monitoring or reintroduction of these species.