Warming appears as the main risk of non-adaptedness for western Mediterranean relict fir forests under expected climate change scenarios.

Circum-Mediterranean firs are considered among the most drought-sensitive species to climate change. Understanding the genetic basis of trees' adaptive capacity and intra-specific variability to drought avoidance is mandatory to define conservation measures, thus potentially preventing their extinction. We focus here on and , both relict tree species, endemic from south Spain and north Morocco, respectively. A total of 607 samples were collected from eight nuclei: six from Spanish fir and two from Moroccan fir. A genotyping by sequencing technique called double digestion restriction site-associated DNA sequencing (ddRAD-seq) was performed to obtain a genetic matrix based on single-nucleotide polymorphisms (SNPs). This matrix was utilized to study the genetic structure of populations and to carry out selection signature studies. In order to understand how Spanish fir and Moroccan fir cope with climate change, genotype-environment associations (GEAs) were identified. Further, the vulnerability of these species to climate variations was estimated by the risk of non-adaptedness (RONA). The filtering of the assembly of provided 3,982 SNPs from 504 out of 509 trees sequenced. Principal component analysis (PCA) genetically separated Grazalema from the rest of the Spanish populations. However, F values showed significant differences among the sampling points. We found 51 potentially under selection. Homolog sequences were found for some proteins related to abiotic stress response, such as dehydration-responsive element binding transcription factor, regulation of abscisic acid signaling, and methylation pathway. A total of 15 associations with 11 different were observed in the GEA studies, with the maximum temperature of the warmest month being the variable with the highest number of associated . This temperature sensitivity was also supported by the risk of non-adaptedness, which yielded a higher risk for both and under the high emission scenario (Representative Concentration Pathway (RCP) 8.5). This study sheds light on the response to climate change of these two endemic species.