Genetic structure of Tunisian natural carob tree (Ceratonia siliqua L.) populations inferred from RAPD markers

• Seven RAPD markers were used to assess the genetic diversity and structure of ten Tunisian natural Ceratonia siliqua L. populations from different geographic and bioclimatic zones. • The species maintain a high diversity within population as estimated by the percentage of polymorphic loci and Shannon’s index (P% = 76.31, \(\bar H'_{pop} = 0.569\)). The range of variation between populations was large. Populations from the upper semi-arid bioclimates, with more continuous distribution area showed the highest level of variation. • A high genetic differentiation among populations (ΦST = 0.250 and \(\bar G_{ST} = 0.347\)), as a result of population isolation was revealed. Nevertheless, the genetic structure is in accordance with bioclimate indicating that ecological factors also should influence differentiation. Populations from the sub-humid, upper semi-arid and mean semi-arid zones clustered together and were distinct from those of the lower semi-arid ones. • Conservation strategy should be made according to the level of polymorphism within population and bioclimate.