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Chamaerops humilis is decreasing in abundance in Mediterranean Europe, which has induced the European community to call for its protection in Special Areas of Conservation. However, information about its genetic and morphological variability, which is crucial to the development of any conservation strategies, is insufficient. The present study aimed to investigate the genetic and morphological variability of C. humilis in Sicily, which was selected as a model because of the high number of dense populations. The relationships between morphological traits and climatic variables were studied to highlight patterns of adaptation to the environment, along with the genetic similarity among the populations. Ten natural populations were sampled, analyzed using 28 specifically designed SSR primers, and evaluated based on 29 morphological traits. The populations were clustered similarly based on genetic and morphological traits. Heterozygosity was high and inbreeding coefficients were low. These results, along with higher intra-than inter-population differentiation, suggest that C. humilis populations in Sicily differentiated from a common ancestor and that inter-population variation arose from secondary evolution processes induced by ecological adaptation. The correlations between climatic variables and morphological traits suggest that the morphological adaptation to arid environments depends more on summer temperatures than on evapotranspiration or rainfall and that autumn and winter temperatures are determinants of the species establishment at new sites. Considering the response of C. humilis to seasonal temperatures, the present results indicate this species as a candidate for tracking climatic changes in Europe. Further studies are needed to highlight the adaptation of C. humilis to cold environments. Palaeo-climatological and - ecological studies could help clarify its strategies for the colonization of new sites. (C) 2014 The Linnean Society of London