Genetic diversity and population structure of Pinus halepensis Mill. in Jordan revealed by simple sequence repeats

Key message Pinus halepensis populations in Jordan maintained a moderate level of genetic diversity with considerable intra-population than inter-population differentiation due to long-distance zygotic and gametic gene flows among populations. The genetic diversity and structure of 156 germplasm samples collected from four natural and five planted Pinus halepensis Mill. populations in Jordan were investigated using simple sequence repeat markers. These fragmented stands represent the easternmost edge of the species natural range of distribution in the Mediterranean basin. Our study revealed relatively high expected heterozygosity and Shannon's diversity index (He = 0.574, I = 1.124). Genetic diversity parameters, Na, Ne, He, and I slightly increased in planted populations compared to natural populations. The AMOVA and population genetic differentiation index (Fst) analysis revealed higher level of intra-population differentiation than inter-population differentiation. The UPGMA cluster analysis and genetic structure analysis revealed two sub-groups, which were not consistent with the geographic distribution pattern. Furthermore, the population genetic distance was not correlated with geographic distance (rxy = - 0.507; p = 0.197; R-2 = 0.2568; y = 60.323x + 8.7366). It can be concluded that Jordan's Aleppo pine populations maintained a moderate level of genetic diversity with marked intra-population than inter-population differentiation. The low genetic differentiation among natural populations can be attributed to an effective gene flow among populations.