Genetic diversity and structure of Sideritis raeseri Boiss. & Heldr. (Lamiaceae) wild populations from Balkan Peninsula

•Sideritis raeseri wild populations are genetically different and distinct from each other.•Higher inter- than intra-population diversity indicates isolation and differentiation.•There is a low positive correlation of geographic and genetic distance.•Landscape morphology and high altitude prevent gene flow among nearby populations.•Different wild populations represent unique genetic resources and their conservation is important.