The current and future potential geographical distribution of Nepeta crispa Willd., an endemic, rare and threatened aromatic plant of Iran: Implications for ecological conservation and restoration
Nepeta crispa Willd. is a very rare medicinal plant that grows in a very limited habitat in western Iran. In recent years, due to climate change, many plants have become endangered, which poses a very serious threat to very rare species such as N. crispa Willd. In the present study, we aimed to model the current and future potential geographical distributions and identify the most relevant environmental factors influencing the distribution of N. crispa Willd. an endemic plant species in west of Iran. The species distribution was modeled with the maximum entropy model by using presence data (160 sampling points) and a total of 15 climatic and environmental variables. To predict possible shifts in the geographical distribution due to climate change, we used the Representative Concentration Pathway (RCP) 2.6 and RCP 8.5 for 2050 and 2070 for two Global Climate Models (GCMs). The jackknifing method was used to evaluate the contribution of the environmental variables to the model. We found that elevation, annual mean temperature, geology and precipitation of the driest quarter were the most important variables in determining the habitat of N. crispa. The species habitat suitability maps and models were efficient in predicting the habitat suitability distribution for N. crispa in the current conditions with an Area Under the ROC Curve (AUC) of 0.983. Our modeling approach also demonstrated that climate change would expand the habitat range of N. crispa in the Alvand mountain areas in Iran towards higher elevation (above 2000 m.a.s.l). Conservation measures should therefore predominantly concentrate on the elevation range between 2000 and 3500 m.a.s.l. Knowledge of current distribution of the N. crispa and predicting its potential future geographical distribution under different climate change scenarios provide useful information for conservation actions in Iran.