Molecular phylogeny and genetic diversity of Tunisian Quercus species using chloroplast DNA CAPS markers

Chloroplast DNA variation was studied in five evergreen Quercus species from the Western part of Tunisia using Cleaved Amplified Polymorphic Sequence (CAPS) technique. Five primer pair/endonuclease combinations have been used. Chlorotypes of Quercus species have been identified. The enzyme HinfI was more efficient in detecting polymorphism in oak species than TaqI. The phenogram showed five groups defining the five studied oak species: suber group, afares group, coccifera group, canariensis group and ilex group. The topology of phenogram showed that the classification depends only on species and independently of their geographic origin. The principal component analysis (ACP) corroborated the results of the tree branching and confirmed the existence of five species groups. Our results showed a genetic proximity between Quercus afares and Quercus coccifera species that may be due to temperature tolerance or the demographic history of these species. Nevertheless, a high value of GST calculated (GST = 1), suggesting that the maximum of variation is maintained among oak species. This result was confirmed by the low value of the genetic diversity within species (hS = 0), the value obtained of the total genetic diversity (hT = 0.378) and the absence of gene flow between species (Nm = 0). A high genetic proximity has been registered between Q. afares, Quercus suber and Quercus canariensis. Moreover, Q. afares shared the chlorotype of Q. suber and Q. canariensis which suggests its hybrid origin.