Three natural populations of Atriplex halimus, located in three different climatic contexts, were studied using leaf characteristics (leaf area, leaf length-to-maximum-width ratio, average width of the leaves and leave-to-branch ratio) and isoenzymatic markers. The study showed the existence of a highly significant phenotypical variability. This variability is all the more significant, as populations are geographically distant and located in different climates. The gradual character of this morphological variability, along a climatic gradient, indicates that it is almost a clinical differentiation. Clones obtained from semi-woody cuttings taken on the level of each population and placed in a common parcel have maintained the same leaf characteristics as the population sources, suggesting the genetic origin of this variability. The study of four isoenzymatic systems confirms the existence of this variability. Thus, the percentage of polymorphic loci (P), the expected heterozygosity (He) and the mean number of alleles per locus (A) are of 77.52%, 0.319, and 1.99, respectively. The genetic diversity index (Fst) obtained is 0.089.