Gene flow among different taxonomic: evidence from nuclear and cytoplasmic markers in Cedrus plantation forests

Hybridization and introgression are important natural evolutionary processes that can be successfully investigated using molecular markers and open-and controlled-pollinated progeny. In this study, we collected open-pollinated seeds from Cedrus atlantica, C. libani and C. libani x C. atlantica hybrids from 3 French plantation forests. We also used pollen from C. libani and C. brevifolia to pollinate C. atlantica trees. The progeny were analyzed using 3 different types of molecular markers: RAPDs, AFLPs and cpSSRs. Chloroplast DNA was found to be paternally inherited in Cedrus from the progeny of controlled crosses. Heteroplasmy, although possible, could not be undoubtedly detected. There was no indication of strong reproductive isolating barriers among the 3 Mediterranean Cedrus taxa. Gene flow between the C. atlantica and C. libani accounted for 67 to 81% of viable open-pollinated seedlings in two plantation forests. We propose that Mediterranean Cedrus taxa should be considered as units of a single collective species comprising two regional groups, North Africa and the Middle East. We recommend the use of cpSSRs for monitoring gene flow between taxa in plantation forests, especially in areas where garden specimen of one species are planted in the vicinity of selected seed stands and gene conservation reserves of another species.