Inter-specific relationships among two Tunisian <i>Thymus</i> taxa: <i>Thymus capitatus</i> Hoffm. et Link. and <i>Thymus algeriensis</i> Boiss. et Reut. using molecular markers

Abstract

Genetic relationships between two sympatric species Thymus capitatus Hoffm. et Link. and Thymus algeriensis Boiss. et Reut. (Thymus hirtus Willd. subsp. algeriensis Boiss. et Reut.) were assessed using random amplified polymorphic DNA (RAPD) markers. Eighteen natural populations from different geographical and bioclimatic zones were evaluated. The seven selected primers generated 121 RAPD markers for T. capitatus (103 polymorphic; P = 85.12%) and 154 for T. algeriensis (141 polymorphic; P = 91.56%). The genetic diversity within T. capitatus and T. algeriensis populations based on Shannon’s index was high (H’_pop = 0.303 and 0.307, respectively). A high genetic differentiation was revealed (G_ST = 0.359 and Φ_ST = 0.284 for T. capitatus, G_ST = 0.335 and Φ_ST = 0.296 for T. algeriensis). The large proportions of the genetic variation were observed within populations for the two studied taxa. A high genetic population’s structure was also estimated by a principal component analysis (PCA). Unweighted pair-group method using arithmetic average (UPGMA) cluster analysis based on Nei and Li's coefficient among populations identified that T. algeriensis and T. capitatus populations were clustered into two distinct groups. The high genetic divergence between the two species corroborates their taxonomic status.

Keywords: Genetic diversity, inter-specific relationships, molecular markers, Thymus capitatus, Thymus algeriensis