The Strait of Gibraltar (SG) is reputed for being both a bridge and a geographic barrier to biological exchanges between Europe and Africa. Major genetic breaks associated with this strait have been identified in various taxa, but it is unknown whether these disjunctions have been produced simultaneously or by independent biogeographic processes. Here, the genetic structure of five conifers distributed on both sides of the SG was investigated using mitochondrial (nad1 b/c, nad5-1, nad5-4 and nad7-1) and chloroplast (Pt1254, Pt15169, Pt30204, Pt36480, Pt71936 and Pt87268) DNA markers. The distribution of genetic variation was partially congruent between types of markers within the same species. Across taxa, there was a significant overlapping between the SG and the genetic breaks detected, especially for the four Tertiary species surveyed (Abies pinsapo complex, Pinus nigra, Pinus pinaster and Taxus baccata). For most of these taxa, the divergence of populations across the SG could date back to long before the Pleistocene glaciations. However, their strongly different cpDNA G(ST) and R(ST) values point out that they have had dissimilar population histories, which might include contrasting amounts of pollen-driven gene flow since their initial establishment in the region. The fifth species, Pinus halepensis, was genetically depauperated and homogenous on both sides of the SG. A further analysis of nuclear DNA sequences with coalescent-based isolation with migration models suggests a Pleistocene divergence of P. halepensis populations across the SG, which is in sharp contrast with the pre-Pleistocene divergence dates obtained for P. pinaster. Altogether, these results indicate that the genetic breaks observed across this putative biogeographical barrier have been produced by independent evolutionary processes related to the biological history of each individual species instead of a common vicariant phenomenon.

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-Pinus pinasterAit. is the main species used for reforestation in Morocco, both in mountain and low lands areas. However, little information is available about its intraspecific variation and adaptability in this range. This work studied the morphological variation of nine native populations, covering the distribution area of maritime pine in Morocco (Rif, Middle Atlas and High Atlas). Thirteen morphological and anatomical traits from cones (length and width), seeds (length, width, thickness and weight), seed wings (length and width) and needles (length, width, thickness and the number of stomata rows on the dorsal and convex faces of the needle) were measured in 232 trees. A Principal Component Analysis was used to explain the variation observed in four principal components related to cone (PCA3), seed (PCA1) and needle (PCA2 and PCA4) traits. Variability in morphological traits was high in Moroccan populations of maritime pine and significant differences among populations were found. Moreover, cone and needle traits showed clinal variation responding to latitude/altitude gradients. A hierarchical classification of all populations led to the formation of three major groups: (i) Mediterranean coastal populations, (ii) southeastern Rif, composed only by one population and (iii) the rest of populations, widely distributed through Moroccan maritime pine range. maritime pine / geographic variation / morphological traits / natural populations / Mediterranean plants Résumé -Variation des caractères morphologiques des populations naturelles du pin maritime (Pinus pinaster Ait.) au Maroc. Pinus pinaster Ait. est une espèce forestière habituellement choisie pour le reboisement au Maroc, aussi bien dans la montagne que dans la plaine. Cependant, peu de données sont disponibles sur sa variabilité et adaptabilité intra spécifiques dans ces milieux. Ce travail a permis d'étudier la variabilité morphologique de neuf populations indigènes, couvrant l'aire du pin maritime au Maroc (Rif, Moyen Atlas et Haut Atlas). Treize caractères morphologiques et traits anatomiques des cônes (longueur et largeur), des graines (longueur, largeur, épaisseur et poids), des ailes de graine (longueur et largeur) et des aiguilles (longueur, largeur, épaisseur et le nombre des lignes stomatiques sur les faces dorsales et convexes de l'aiguille) ont été mesurés sur 232 arbres. Une analyse en composantes principales a été employée pour expliquer la variance observée. Les quatre principaux axes correspondent à des caractères liés aux cônes (PCA3), aux graines (PCA1) et aux aiguilles (PCA2 et PCA4). La variabilité des caractères morphologiques est importante dans les populations marocaines de pin maritime et des différences inter populations significatives ont été mises en évidence. D'autre part, les caractéristiques des cônes et des aiguilles ont montré une variation clinale répondant aux gradients de latitude/altitude. La classification hiérarchique basée sur les caractères morphologiques de toutes les populations a conduit à l'individualisa...

Using nuclear simple sequence repeats (nuSSRs), we determined the genetic variability in the natural distribution range of maritime pine (Pinus pinaster) in the western Mediterranean region. We analysed the role of global and significant climatic fluctuations in driving the evolutionary diversification of this species. We attempted to determine the impact of the last glacial maximum (LGM) and human activity on genetic variation and to identify the effect of bottlenecks, admixing, migration, time to the most recent common ancestor (TMRCA), and recent splits. A total of 972 individuals were analysed. The sample represented 27 natural populations from the western Mediterranean region, which encompasses most of the natural range of P. pinaster. Using eight nuSSRs, we analysed genetic diversity indices for each population and group of populations. We also examined the interpopulation structure by the frequency and distance method and investigated genetic barriers, signals of historical demographic fluctuations, phylogeographic structure, admixing, rate of mutation, migration, as well as testing the hypothesis of isolation by distance (IBD). Both cluster analyses showed similar population genetic structure with three genetic barriers that divided the samples into four large groups. Intensive migration was only detected during the period of the last glacial maximum (LGM), which permitted the mutation rate of the markers used to be calculated. The majority of the population was found to exhibit signs of a recent bottleneck and its timing showed a clear northeast-southwest geographic distribution. A clearly defined phylogeographic structure (Nst > Gst and Rst > Gst ) under IBD was established, and showed the highest divergence between groups of populations separated by physical barriers, such as the Strait of Gibraltar, the Mediterranean Sea and the Pyrenees. The high level of intergroup genetic differentiation (ΦIS = 20.26) was attributed to a long historical isolation (which occurred before the last 18 000 years) between the principal maritime pine population groups that occurred due to physical barriers that limited pollen and seed transfer, combined with a minimal effective radius of distribution. The low level of genetic diversity among the populations was combined with genetic drift and a recent bottleneck during the period of human activity. Significant migration across barriers was due to spontaneous phenomena during the LGM, which had no significant impact on the genetic structure owing to its relatively short duration and the fragmented species. The phylogeographic structure under the assumption of IBD was well established for P. pinaster in each of the principal population groups.