Climate Change Impact on the Future Distribution of Rare, Relict and Small Fragmented Populations of Lilium ledebourii in the Hyrcanian Forest

This study aimed to map the historical geographical range of L. ledebourii in the Hyrcanian Forest; assess the current areas inhabited by this species; predict the future geographical distribution of this rare species under various climate change scenarios; and determine the main climatic factors associated with the distribution pattern of L. ledebourii. Lilium ledebourii is a rare plant with a very limited and fragmented distribution in the Hyrcanian Forest. A total of 19 spatial points were utilized to model the potential distribution of L. ledebourii under both current and projected climate conditions. Bioclimatic variables for present-day conditions were sourced from the CHELSA database, while data for the Last Glacial Maximum were obtained from the NCAR-CCSM4 model. For future climate scenarios, variables were derived from three different models across two distinct projections. The most important variables were precipitation in the warmest quarter, precipitation in the coldest quarter, and precipitation seasonality. The present potential range of the species covers 40,909 km2, forming a long strip in the Hyrcanian area with the highest suitability in the mountains. During the LGM, the species potential range was approximately 16% greater than the current range. Under future conditions, the potential range of L. ledebourii is likely to be drastically reduced, and suitability will decrease significantly. According to the morphological spatial pattern analysis, the future potential range of L. ledebourii will be fragmented in both tested scenarios. The connections between these core areas will be very restricted. Considering the shrinking of the habitat areas of L. ledebourii due to climate change and the high vulnerability of this species in its habitat (grazing, steep slopes, and soil erosion), ex situ conservation could represent the most effective approach for securing the long-term survival of L. ledebourii within the Hyrcanian forest.