ABSTRACT Aim Understanding the evolutionary history and demographic dynamics of narrow‐ranged endemics is essential for predicting their future under climate change. We investigated the origins, population trajectories, and conservation outlook of three endemic spurges ( Euphorbia gayi , E. valliniana , E. variabilis ) restricted to the south‐western Alps, Corsica, and Sardinia. Location South‐western Alps, Corsica, Sardinia. Methods We used restriction site‐associated DNA (RAD) sequencing data to infer phylogenetic relationships, population structure, and long‐term effective population size ( N e ) dynamics through demographic modelling. To assess vulnerability under climate change, we combined genomic insights with species distribution modelling (SDM) across past (Last Glacial Maximum), present, and future (ssp126, ssp370, ssp585) climate scenarios. Results Genomic analyses revealed mid‐Pleistocene divergence of E. gayi and evidence of long‐distance dispersal underlying the origin of E. variabilis . All three species showed strong genetic structure and limited connectivity among populations, alongside a long‐term decline in N e . SDMs predicted substantial range contractions under future warming, with losses of up to 98% of suitable habitat by 2100 under the ssp585 scenario. Even under optimistic projections (ssp126), range reduction was pronounced, particularly for the small and isolated Corsican and Sardinian populations of E. gayi . Main Conclusions Our integrative genomic and ecological modelling approach highlights the vulnerability of three narrow‐ranged alpine and montane endemics to ongoing climate change. Persistent demographic decline, limited population connectivity, and severe habitat loss together place these taxa at high risk of local or complete extinction. These findings emphasise the need for urgent conservation measures to safeguard endemic Mediterranean mountain plants under future climate change.
Heimer et al. (Sun,) studied this question.