Genetic diversity and population structure in natural populations of Moroccan Atlas cedar (Cedrus atlantica; Pinaceae) determined with cpSSR markers

Atlas cedar (Cedrus atlantica) is an ecologically and economically important forest tree species of northern Africa and is considered one of the endangered conifer species in the region. Chloroplast microsatellites (cpSSR) were used to study genetic variation within and among populations and geographical structure in natural populations of C. atlantica throughout its entire distribution range in Morocco. A total of 25 chloroplast haplotypes and 66 cpSSR alleles were found among 162 individuals. The cpSSRs indicate that C. atlantica appears to maintain a high level of genetic diversity (mean H(e) = 0.95), as observed in most coniferous species. Values of mean pairwise distance within a population (D(2)(SH)) were related to the size and location of the populations. AMOVA analysis showed that most of the variation in C. atlantica occurs within populations and confirmed the general tendency of gymnosperms to display lower values of population differentiation than angiosperms. The distance-based clustering method (PCoA and neighbor-joining analysis) and the geographical structure revealed a poor structure among the six populations of Cedrus atlantica. Also, a Mantel test indicated a weak correlation between geographic and genetic distances (P = 0.106, r = 0.363). These results are also interpreted in the context of postglacial history of the region plus human impacts.