Graellsia isabellae (Lepidoptera, Saturniidae) is an emblematic threatened Lepidoptera species, found in mountain ranges of Spain and Alps. This moth is potentially impacted by climate change and dieback of its main host plant Scots pine (Pinus sylvestris). Our study was focused on the French Alpine population, because of its isolation and low genetic diversity as shown in a previous analysis based on mitochondrial DNA and microsatellite data. In order to better characterize the French population for conservation, a RADseq approach was used for 62 individuals, making it possible to obtain a large number of nuclear loci. The genetic variations analyzed (3,644 SNPs) confirm the strong isolation between the Pyrenean (n=8) and the Alpine (n=53) populations, but also reveal a sub-structure in the Alps. Basic genetic statistics also confirmed the low genetic diversity of the French population. To assess the environmental constraints affecting its distribution, a niche modeling approach was used, by incorporating climatic variables as well as the distribution of its host plant. This revealed that the potential distribution area is currently relatively limited. Projections of the evolution of its niche in the future, up to 2050, show a change in niche suitability that could have negative consequences for the survival of the French population and implications for the conservation strategy.