The Role of Hybridization on the Adaptive Potential of Mediterranean Sclerophyllous Oaks: The Case of the Quercus ilex x Q. suber Complex

Abstract

Gene flow among closely related species is a not so unusual event, especially in plants. Hybridization and introgression have probably played a relevant role in the evolutionary history of the genus Quercus, for instance in the post-glacial northwards migration of European white oaks. In the same way, hybridization between the Mediterranean sclerophyllous oaks Q. ilex and Q. suber could have been determinant for the survival of the latter species during glaciations. In this chapter, evidences of the ancient introgression between these two species are revised, as well as estimations of current hybridization rates, which are very likely underrated. Pre-zygotic and post-zygotic limitations to introgression between Q. suber and Q. ilex are described. Finally, the effects of hybridization and introgression on cork quality, and the suitability of Q. ilex-Q. suber as a model system for the study of introgression and the maintenance/restoration of species boundaries within the genus are briefly discussed.