Genetic diversity in high-mountain Thymus species in Bulgaria revealed by ISSR genetic markers

High mountain populations of the plant species possess particular interest from both evolutionary and conservation points of view. The mode of distribution, limited gene flow and severe environmental conditions act as evolutionary forces shaping the level and distribution of genetic diversity within and among populations. The paper reports results of a study on four populations of Thymus praecox aggr., including the taxa T. vandasii and T. jankae. Two populations are located in Rila Mts (Belmeken dam and Yastrebets), one – in Pirin (Vihren hut) and one – in the Rhodopes (Perelik hut).  Eleven inter simple sequence repeat (ISSR) markers were applied to document the genetic diversity within and among populations. The level and distribution of the diversity correspond to the values reported in other studies on the species of the genus Thymus and other species with similar life-history characteristics. The populations from Rila and Pirin were genetically closer to each other, while the population from the Rhodopes was the most differentiated. The results are discussed in the light of the conservation and sustainable use of the species resources.