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International audience; Carob (Cetatonia siliqua L.) is a well-known Mediterranean tree whose domestication was coetaneous to that of the first trees (eg. olive, fig) probably in the Middle-East. Since then, carob has played a crucial role in Mediterranean societies due to its edible fruits used for cattle forage and subsistence agriculture. Carob plants are able to grow on stressful rocky soils increasing the socio-economic value of many Mediterranean dry lands. Despite its economic importance, the origins and history of carob populations are still under debate. Since De Candolle, the wildness of carob populations has been questioned on the basis of paleo-botanical, archeological and philological evidences and , unfortunately, the scarce studies on the ecology and genetic diversity of wild populations have not thrown much light on this topic. The extremely low cold-stress tolerance of carob plants constituted the main argument against a long-term persistence of natural populations throughout Pleistocene glaciations in the Mediterranean. Under this scenario, the current distribution would be explained by human dissemination. However, a global phylogeographic study covering the entire distribution of carob is still lacking. In this context, we aimed at exploring the two main hypotheses about the origin of carob populations: their possible persistence in unknown refugia during the Pleistocene or their putative naturalization after human dissemination throughout the Mediterranean from a single origin. We used Environment Niche Modeling (ENM) under present and past climatic conditions (MidHolocene – aprox. 6 kya; Last Glacial Maximum, LGM – aprox. 22 kya; and Last Interglacial Maximum, LIG – aprox. 120-140 kya) to investigate the potential range changes that carob could have undergone driven by climatic oscillations. Additionally, we sequenced three plastid regions from both natural and cultivated populations covering the whole current distribution of carob to explore its phylogeography based on coalescent methods. Our results point towards two distant and separated two distinct and separated phylogroups atat southern boundaries of carob range during LIG, which left a strong genetic footprint within carob natural populations. This was followed by a reduction of the potential distribution area during LGM, which subsequently expanded during MidHolocene up to the current Mediterranean known distribution of carob. The current potential distribution modeled for carob is extremely restrictive to the coastal areas of the Mediterranean, and it actual distribution is probably linked to strong selection pressures at the margins of its range. Climatic variability and long term persistence within the carob range suggest that evolutionary legacy could be a pivotal factor to take into account in both breeding and reforestation programs.

International audience; Evolutionary theory predicts that organisms with low growth rates, like trees, will be vulnerable to face rapid environmental changes. Despite its economic importance, the long-term history of carob tree is still under debate. Since De Candolle, the wildness of carob populations has been questioned on the basis of paleo-botanical, archeological and philological evidences and, unfortunately, the scarce studies on the ecology and genetic diversity of wild populations have not thrown much light on this topic. In this context, we aimed at exploring the two main hypotheses about the origin of carob populations: their possible persistence in unknown refugiaduring the Pleistocene or their putative naturalization after human dissemination throughout the Mediterranean from a single origin. Ecological marginality and geographic persistence through time were analyzed on the basis of floristic surveys and environment niche modeling respectively. Additionally, we sequenced nuclear and plastid regions from both natural and cultivated populations covering the whole current distribution of carob to explore its phylogeography based on coalescent methods. Our results point towards a past bottleneck which left two phylogroups within natural carob populations. The current potential distribution modeled for carob is extremely restrictive to the coastal areas of the Mediterranean, and its actual distribution is probably linked to strong selection pressures at the margins of its range. In the framework of the DYNAMIC project (Deciphering sYmbiotic Networks in cArob-based MedIterranean agro-eCosystems) these biogeographical insights will be used as a baseline to analyze relationships between the carob evolutionary legacy and community ecology.

Mediterranean Geoarchaeology Workshop, Shaping the Mediterranean basin: islands, coastlines and cultures across time

Black rats, Rattus rattus, and mat-forming iceplants, Carpobrotus aff. acinaciformis and Carpobrotus edulis, are pervasive pests on Mediterranean islands. Their cumulative impacts on native biotas alter the functioning of island ecosystems and threaten biodiversity. A report is given here of the first attempt to eradicate both taxa from a protected nature reserve in south-eastern France (Bagaud Island). In order to minimise unwanted hazardous outcomes and produce scientific knowledge, the operations were embedded in a four-step strategy including initial site assessment, planning, restoration and monitoring.[br/]Trapping, which resulted in the removal of 1923 rats in 21 045 trap-nights, made it possible to eliminate a substantial proportion of the resident rat population and to reduce the amount of rodenticide delivered in the second stage of the operation. Forty tons of Carpobrotus spp. were manually uprooted from a total area of 18 000 m(2) ; yet careful monitoring over a decade is still required to prevent germinations from the seed bank.[br/]Two years after the beginning of the interventions, both eradication operations are still ongoing. Biosecurity measures have been implemented to reduce reinvasion risks of both taxa. With the long-term monitoring of various native plants and animals, Bagaud Island will become a reference study site for scientific purposes.

In south Morocco, some Olea populations exist with intermediary morphology between the Olea subspecies laperrinei and europaea. This Olea population was ignored for a long time. It received various names including O. maroccana. Recently (2001), based on morphological and molecular data, it was transferred at the subspecific rank. The phenology is introduced here as a new criterion. The main characters of this endemic Moroccan Olea are given. The two subspecies europaea and maroccana are in sympatry. This is an original situation and raise questions on their evolution., Au sud du Maroc, existent des populations d'Olea dont la morphologie est intermédiaire entre la sous-espèce laperrinei et la sous-espèce europaea. Longtemps ignoré ou négligé, ce taxon d’Olea a reçu des noms divers, dont celui de O. maroccana. Ce n’est que récemment, en 2001, que la morphologie et le marquage moléculaire ont permis de considérer cet olivier comme sous-espèce de l’Olea europaea. La phénologie est introduite ici comme un critère nouveau. Les principales caractéristiques de cet olivier endémique du Maroc sont exposées. Les deux sous-espèces europaea et maroccana existent en sympatrie, ce qui est une situation originale et interroge sur leur évolution., Breton Catherine,Médail Frédéric,Bervillé André. Olea europaea subsp. maroccana : cette sous-espèce est-elle justifée ?. In: Le Journal de botanique, n°30, 2005. pp. 19-25.

The insular systems are very vulnerable to various disturbances which can induce some important floristical changes. The aim of this study is to analyse the flora changes which occurred within a 60 years period (between 1938 and 1997) on the two main islands, Pomègues and Ratonneau of the Frioul archipelago (Marseille, south-east France). We performed both a taxonomic and a functional analysis of the plant data. The functional approach was made by the study of growth form, dispersal, Grime strategy, and biogeographical type of each plant species. We focused particularly on the plant species newly established on the archipelago. The main results were : i) a prevalence of therophytic plant species within the newly established plants, ii) a constancy in the part made by each dispersal mode, with a prevalence of taxa dispersed by wind, iii) an increase in the part made by ruderal species, notably on Ratonneau island, iv) a slight decrease of mediterranean plant species on Ratonneau island. Changes which have occurred in the plant species seem to be due to several recent anthropogenic factors. These disturbances are particularly acute on Ratonneau island and are mainly the result of the building of ‘Port Frioul’ residential area, Les systèmes insulaires constituent des systèmes très sensibles aux perturbations. Celles-ci peuvent, en effet, y provoquer des modifications floristiques plus ou moins importantes. La présente étude vise à analyser les changements subis par la flore de l’archipel méditerranéen du Frioul (Marseille) en l’espace de 60 ans. Pour cela a été réalisée une comparaison des cortèges floristiques, entre 1938 et 1997, sur les deux principales îles de l’archipel : Ratonneau et Pomègues. Les données ont été traitées au niveau fonctionnel, en attribuant, à chaque espèce végétale, son type biologique, son mode de dissémination, sa stratégie démographique et son type biogéographique. Les espèces nouvellement implantées sur l’archipel ont servi de descripteur privilégié. Ainsi, nous avons constaté : i) une prépondérance des thérophytes dans les taxons nouvellement implantés, ii) une relative constance dans les pourcentages des différents types de dissémination, avec une prédomi nance des taxons anémochores, iii) une tendance à l’augmentation des taxons rudéraux, plus marquée sur Ratonneau que sur Pomègues, iv) une légère diminution des taxons de type méditerranéen sur Ratonneau. Ces changements des caractéristiques fonctionnelles des cortèges floristiques sont dus à un faisceau de perturbations, affectant surtout Ratonneau, et principalement lié à l’activité humaine importante autour de la zone d’habitations de Port-Frioul., Bonnet Véronique,Vidal Éric,Médail Frédéric,Tatoni Thierry. Analyse diachronique des changements floristiques sur un archipel méditerranéen péri-urbain (îles du Frioul, Marseille). In: Revue d'Écologie (La Terre et La Vie), tome 54, n°1, 1999. pp. 3-18.

The identification of past glacial refugia has become a key topic for conservation under environmental change, since they contribute importantly to shaping current patterns of biodiversity. However, little attention has been paid so far to interglacial refugia despite their key role for the survival of relict species currently occurring in climate refugia. Here, we focus on the genetic consequences of range contraction on the relict populations of the evergreen shrub Myrtus nivellei, endemic in the Saharan mountains since at least the end of the last Green Sahara period, around 5.5 ka B.P. Multilocus genotypes (nuclear microsatellites and AFLP) were obtained from 215 individuals collected from 23 wadis (temporary rivers) in the three main mountain ranges in southern Algeria (the Hoggar, Tassili n'Ajjer and Tassili n'Immidir ranges). Identical genotypes were found in several plants growing far apart within the same wadis, a pattern taken as evidence of clonality. Multivariate analyses and Bayesian clustering revealed that genetic diversity was mainly structured among the mountain ranges, while low isolation by distance was observed within each mountain range. The range contraction induced by the last episode of aridification has likely increased the genetic isolation of the populations of M. nivellei, without greatly affecting the genetic diversity of the species as a whole. The pattern of genetic diversity observed here suggests that high connectivity may have prevailed during humid periods, which is consistent with recent paleoenvironmental reconstructions.

International audience; The identification of past glacial refugia has become a key topic for conservation under environmental change, since they contribute importantly to shaping current patterns of biodiversity. However, little attention has been paid so far to interglacial refugia despite their key role for the survival of relict species currently occurring in climate refugia. Here, we focus on the genetic consequences of range contraction on the relict populations of the evergreen shrub Myrtus nivellei, endemic in the Saharan mountains since at least the end of the last Green Sahara period, around 5.5 ka B.P. Multilocus genotypes (nuclear microsatellites and AFLP) were obtained from 215 individuals collected from 23 wadis (temporary rivers) in the three main mountain ranges in southern Algeria (the Hoggar, Tassili n'Ajjer and Tassili n'Immidir ranges). Identical genotypes were found in several plants growing far apart within the same wadis, a pattern taken as evidence of clonality. Multivariate analyses and Bayesian clustering revealed that genetic diversity was mainly structured among the mountain ranges, while low isolation by distance was observed within each mountain range. The range contraction induced by the last episode of aridification has likely increased the genetic isolation of the populations of M. nivellei, without greatly affecting the genetic diversity of the species as a whole. The pattern of genetic diversity observed here suggests that high connectivity may have prevailed during humid periods, which is consistent with recent paleoenvironmental reconstructions.

De l’olivier à l’oléastre : origine et domestication de l’Olea europaea L. dans le Bassin méditerranéen Keywords : VEGETAL PRODUCTIONS, NATURAL RESOURCES AND ENVIRONMENTRésumé : L’olivier occupe la 24 e place des 35 espèces les plus cultivées dans le monde. La diversité phénologique des cultivars est remarquable et l’intérêt économique de l’espèce est majeur. Pourtant peu d’études ont porté sur la domestication de l’olivier et sur les relations entre l’olivier et sa forme sauvage, l’oléastre. Les marqueurs moléculaires rendent possible l’étude de la structure génétique des cultivars, des flux géniques et des relations entre la forme cultivée et sauvage. L’analyse de la diversité actuelle de la sous-espèce europaea d’Olea europea permet de remonter le temps et d’analyser les mécanismes qui ont conduit à cette diversité. Les processus utilisés donnent un panorama de la diversité après les glaciations et permettent de situer globalement les zones refuges qui apparaissent nombreuses et génétiquement très structurées. La comparaison avec la connaissance populaire montre que, chez cette espèce, l’histoire a été enjolivée, probablement pour combler l’absence de données historiques. L’origine de l’olivier à partir de l’oléastre ne fait plus de doute à l’est comme à l’ouest de la mer Méditerranée. Cependant, la diversité de l’oléastre et de l’olivier est maximale à l’ouest. L’archéologie confirmant la présence de l’oléastre à l’ouest, l’origine de la sous-espèce europaea est donc à reconsidérer, The olive tree is the cultivated form of the wild oleaster, both of which belong to the subspecies europaea of Olea europaea and are naturally distributed all around the Mediterranean Sea. In addition to these, some trees escaped from cultivation resemble oleasters by their physiognomy. No specific morphologic marker unambiguously differentiates the three forms. Olive cultivars today show a wide diversity in their morphology and phenology. Olives are important economically in Mediterranean countries, and olive oils carrying the taste and aroma of the fruit are the base of a new gastronomy also economically significant. Olive trees fashion landscapes and prevent erosion, and a social culture is associated with their products. Oleasters are endangered due to recurrent gene flow from the olive tree, human impact on forests and climate change. Olive cultivars result from a long process of selection in diverse environments that have had different cultural practices and traditions ever since the olive tree began accompanying human migration in the Neolithic period. The first domestication had occurred by -5800 B.P. around the eastern Mediterranean basin. Olive cultivars are deeply differentiated according to ultimate use — for oil, table or mixed. Their origins are unknown and the country of origin is only an indication of where they come from. Cultivars and oleasters are wind-pollinated and outcrossing is the rule. Molecular markers have recently made it possible to study the diversity of olive trees and thus to attempt to verify myths and beliefs about their origins. Relations between cultivars can now be established with several types of markers. Domestication events must have appeared in several sites around eastern and western Mediterranean localities since cultivars have inherited cytotypes of local oleasters, and this probably occurred simultaneously. Human migrations displaced cultivars, leading to gene flow: local oleasters generate new forms and new cultivated genotypes. Cytoplasmic markers show at least four separate origins of olive trees from oleasters, and SSRs show at least seven. Molecular markers have enabled us to show that each cultivar corresponds to one clone with a few exceptions. This means that cultivars were propagated from a single tree, with some exceptions that may be due to mixing two or three sister progenies of one tree. Although oleasters originate from seven different refuge areas, gene flow caused by cultivar displacement has disturbed this structure. Some cultivars also have their origin in some of these primary populations but others appeared as hybrids between two or three of these zones. This suggests that gene flow occurred between local oleasters and cultivars introduced by human migrations

To understand the history and dynamics of the plant cover in a particular place, the carrying out of paleo-ecological and phyto-historical studies constitutes a vital first step. Such investigations in fact make it possible to retrace the evolution of the vegetation in relation to climatic change and/or human activity, thereby supplying indispensable evidence of the sites’s potential plant cover. Later, such knowledge represents an essential tool for guiding decisions in forestry management aimed at sustainable development or biological conservation. The Maures mountain massif, periodically the victim of wildfire, possesses a value as ‘natural heritage’ that has been recognised by the WWF which recently classified the area among the ten most important woodland ensembles of the Mediterranean Rim. Even so, the dynamics and history of the areaduring the Holocene period are largely unknown. In this context, the aim of this study was to reconstitute the history and dynamics of the woody vegetation in one part of the Maures massif and to assess the role of wildfire in the establishment of patterns of plant cover.The study, based on the analysis of charred wood/coals (pédoanthracologie to use the French term), has made it possible to highlight different phases in the evolution of the woody vegetation over time. A mixed oak forest (Quercus pubescens, present as of 7,000 BP, Q. suber, present as of 8,000 BP andErica arborea) in which Q. pubescens (downy oak) dominated, formed the plant cover at the height of the Holocene. Such cover is characteristic of an only slightly disturbed, or undisturbed, environment. Thereafter, following on the increasing impact of man on his habitat (clearing for agriculture, fires,grazing, etc.), a cork oak cover, favoured by man, progressively took hold. This forest cover is resistant to wildfire and is accompanied by colonising species or those that re-sprout from coppice. Finally, with the ongoing decline of farming communities, the woodland environment has been closing over, thus becoming favourable to the downy oak and mesophilic tree species., Pour connaître l’histoire et la dynamique de la végétation d’un lieu, la mise en place d’études paléoécologiques et phyto-historiques est une étape primordiale. En effet, ces études permettent de retracer l’évolution de la végétation en relation avec les changements climatiques et/ou l’action de l’homme, ce qui apporte ainsi des témoignages indispensables pour connaître la végétation potentielle d’un lieu. Par la suite, ces connaissances sont un outil essentiel pour orienter les choix de gestion forestière dans une optique de développement durable et de biologie de la conservation. Le massif des Maures, soumis périodiquement aux incendies, possède un intérêt « patrimonial » récemment reconnu par le WWF qui le classe parmi les dix ensembles forestiers majeurs du pourtour méditerranéen. Cependant, la dynamique et l’histoire holocène de ce massif restent méconnues. Dans ce contexte, l’objectif de cette étude est de reconstituer l’histoire et la dynamique de la végétation ligneuse d’un secteur du massif des Maures, et d’évaluer le rôle des incendies dans la mise en place de la végétation. Cette étude, basée sur l’analyse des charbons de bois (la pédoanthracologie), a permis de mettre en évidence différentes phases dans l’évolution de la végétation ligneuse au cours du temps. La chênaie mixte (Quercus pubescens présent depuis 7000 BP, Quercus suber présent depuis 8000 BP et Erica arborea) dominée par le chêne pubescent, constituait la végétation de l’optimum Holocène, caractéristique d’un milieu peu ou pas perturbé. Puis, consécutivement à l’augmentation de l’emprise de l’homme sur son milieu (défrichement pour la mise en culture, feux, pâturages, etc), une suberaie s’est progressivement mise en place car favorisée par l’homme. Cette formation forestière résistante aux feux est accompagnée d’essences pionnières ou rejetant de souche. Enfin, depuis la déprise agricole, le milieu forestier se referme et devient favorable au retour du chêne pubescent et des essences mésophiles., Per conoscere la storia e la dinamica della vegetazione di un luogo, la messa in posto di studi paleoecologicie fito-storici è una tappa primordiale. Difatti, questi studi permettono di descrivere l’evoluzione della vegetazione in relazione coi cambiamenti climatici e/o l’azione dell’uomo ciò che adducce così testimoni indispensabili per conoscere la vegetazione potenziale di un luogo. In seguito, queste conoscenze sono un’arnese essenziale per orientare la scelta di gestione forestale nel punto di vista di sviluppo sostenibile e di biologia della conservazione. Il massiccio dei Maures, sottomesso periodicamente agli incendi, possiede un interesse « patrimoniale » recentemente riconosciuto dal WWF che lo classifica tra i dieci insiemi forestali maggiori del circuito mediterraneo. Tuttavia, la dinamica e la storia olocenica del massiccio rimangono sconosciute. In questo contesto, l’obbiettivo di questo studio è di ricostituire la storia e la dinamica della vegetazione legnosa di una zona del massiccio dei Maures, e di valutare la parte degli incendi nella messa in posto dei modelli di vegetazione. Questo studio, basato sull’analisi dei carboni di legna (la pedoantracologia), ha permesso di mettere in evidenza differenti fasi nell’evoluzione della vegetazione legnosa nel corso del tempo. Il querceto misto (Quercus pubescens presente da 7000 BP, Quercus suber presente da 8000 BP e Erica arborea) dominata dalla roverella, costituiva la vegetazione dell’optimum olocene, caratteristico di un’ambiete poco o non disturbato. Poi, conseguentemente all’aumento dell’influenza dell’uomo sul suo ambiente (dissodamento per la messa in coltura, fuochi, pascoli, ecc), una foresta di sugheri si è messa in posto progressivamente perchè favotita dall’uomo. Questa formazione forestale resistente al fuoco è accompagnata di essenze pionieri o ricacciante da ceppo. Finalmente, sino dall’abandono agricolo, l’ambiente forestale si richiude e diventa favorevole al ritorno della roverella e delle essenze mesofile.