Frédéric Médail

Indian summer monsoon variations could have affected the early Holocene woodland expansion in the Near East

Postglacial expansion of deciduous oak woodlands of the Zagros—Anti-Taurus Mountains, a major biome of the Near East, was delayed until the middle Holocene at ~6300 cal. yr BP. The current hypotheses explain this delay as a consequence of a regional aridity during the early Holocene, slow migration rates of forest trees, and/or a long history of land use and agro-pastoralism in this region. In the present paper, support is given to a hypothesis that suggests different precipitation seasonalities during the early Holocene compared with the late Holocene. The oak species of the Zagros—Anti-Taurus Mts, particularly Quercus brantii Lindl., are strongly dependent on spring precipitation for regeneration and are sensitive to a long dry season. Detailed analysis of modern atmospheric circulation patterns in SW Asia during the late spring suggests that the Indian Summer Monsoon (ISM) intensification can modify the amount of late spring and/or early summer rainfall in western/northwestern Iran and eastern Anatolia, which could in turn have controlled the development of the Zagros—Anti-Taurus deciduous oak woodlands. During the early Holocene, the northwestward shift of the Inter-Tropical Convergence Zone (ITCZ) could have displaced the subtropical anticyclonic belt or associated high pressure ridges to the northwest. The latter could, in turn, have prevented the southeastward penetration of low pressure systems originating from the North Atlantic and Black Sea regions. Such atmospheric configuration could have reduced or eliminated the spring precipitation creating a typical Mediterranean continental climate characterized by winter-dominated precipitation. This scenario highlights the complexity of biome response to climate system interactions in transitional climatic and biogeographical regions.

Valeur prédictive des types biologiques pour la conservation de la flore méditerranéenne.

The validity of Raunkiaers biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.Abstract The validity of Raunkiaer’s biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.The validity of Raunkiaer’s biological types (or life-forms) was tested on native Corsican flora, using criteria of altitudinal distribution and rarity. The biological basis of this classification has been widely confirmed. The analysis of floras from Corsica and Provence revealed the major role played by both altitude and human impact, and also demonstrated the importance of the predictive value of life-forms to plant conservation. In Southeastern France, there are no clear proportional relationships between rarity and extinction percentages. With increasing levels of human activity, rarity percentages are seen to increase for nearly all types. Conversely, extinction percentages exhibit a clear progression only for the most threatened life-forms: bulb and tuber geophytes, therophytes, parasites and especially hydrophytes. Thus, priority should be given to the protection of these 4 herbaceous types, which are found at low altitudes and lack visible vegetative organs during the unfavourable season.

Phylogeography sheds light on the central-marginal hypothesis in a Mediterranean narrow endemic plant.

BACKGROUND AND AIMS Understanding the factors that shape variation in genetic diversity across the geographic ranges of species is an important challenge in the effort to conserve evolutionary processes sustaining biodiversity. The historical influences leading to a central-marginal organization of genetic diversity have been explored for species whose range is known to have expanded from refugia after glacial events. However, this question has rarely been addressed for Mediterranean endemic plants of azonal habitats such as rocky slopes or screes. In this context, this comprehensive study examined molecular and field data from Arenaria provincialis (Caryophyllaceae), a narrow endemic plant of south-eastern France. METHODS Across the whole geographic range, an investigation was made of whether high levels of abundance and genetic diversity (estimated from amplified fragment length polymorphism markers) are centrally distributed, to evaluate the relevance of the central-marginal hypothesis. Phylogeographic patterns inferred from chloroplast DNA (cpDNA) were used, applying Bayesian methods to test the influence of past biogeographic events. Multivariate analysis combining phylogeographic and ecological data was used to reveal the historical and ecological distinctiveness of populations. KEY RESULTS Despite the narrow distribution of A. provincialis, a high level of nucleotide variation is found within cpDNA loci, supporting its persistence throughout the Pleistocene period. The area characterized by the highest genetic diversity is centrally located. Structured phylogeography and Bayesian factor analysis supported the hypothesis that the central area of the distribution was the source of both westward and eastward migrations, probably during arid periods of the Pleistocene, and more recently was a crossroads of backward migrations. By contrast, the two areas located today at the range limits are younger, have reduced genetic diversity and are marginal in the ecological gradients. CONCLUSIONS This study highlights a case of strong population distinctiveness within a narrow range. Phylogeography sheds light on the historical role of the areas centrally situated in the distribution. The current range size and abundance patterns are not sufficient to predict the organization of genetic diversity.

Eradications as scientific experiments: progress in simultaneous eradications of two major invasive taxa from a Mediterranean island

BACKGROUND 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. RESULTS 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. CONCLUSION 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.

Geographical isolation caused the diversification of the Mediterranean thorny cushion-like Astragalus L. sect. Tragacantha DC. (Fabaceae).

Understanding the origin and evolution of Mediterranean vascular flora within the long-term context of climate change requires a continuous study of historical biogeography supported by molecular phylogenetic approaches. Here we provide new insights into the fascinating but often overlooked diversification of Mediterranean xerophytic plants. Growing in some of the most stressing Mediterranean environments, i.e. coastal and mountainous opened habitats, the circum-Mediterranean Astragalus L. sect. Tragacantha DC. (Fabaceae) gathers several thorny cushion-like taxa. These have been the subjects of recent taxonomical studies, but they have not yet been investigated within a comprehensive molecular framework. Bayesian phylogenetics applied to rDNA ITS sequences reveal that the diversification of A. sect. Tragacantha has roots dating back to the Pliocene, and the same data also indicate an eastern-western split giving rise to the five main lineages that exist today. In addition, AFLP fingerprinting supports an old east-west pattern of vicariance that completely rules out the possibility of a recent eastern origin for western taxa. The observed network of genetic relationships implies that contrary to what is widely claimed in the taxonomic literature, it is range fragmentation, as opposed to a coastal-to-mountain ecological shift, that is likely the main driver of diversification.

Genetic diversity and structure of a Mediterranean endemic plant in Corsica (Mercurialis corsica, Euphorbiaceae)

The island of Corsica is a Mediterranean hotspot of plant biodiversity characterized by a high rate of plant endemism, but also by a lack of studies combining genetic diversity and conservation. In Corsica, the dioecious and Corso-Sardinian endemic Mercurialis corsica Cosson (Euphorbiaceae) occurs across a wide ecological gradient, but the number of populations have decreased considerably over the last century. The main aim of this study was to examine the patterns of genetic diversity occurring in the Corsican populations of M. corsica, depending on their location and demographic structure. The rDNA sequences did not show the existence of any polymorphism, whereas the cpDNA sequences revealed the divergence of the western Corsican populations. By contrast, when the AFLP markers were examined, although significant levels of differentiation were detected between populations, no distinct geographical patterns were observed except for the pronounced isolation of the Cap Corse genotypes. No significant correlations were found to exist between population size and the genetic diversity indexes used. The results of this study suggest that M. corsica has undergone a complex gene flow history involving past population admixtures, followed by fragmentation processes resulting in population differentiation but no geographical patterns of isolation. These results support the existence of three evolutive conservation units which have to be monitored in priority to determine whether the current pattern of demographic structure is still declining or has stabilized.

Phylogenetic diversity and genome sizes of Astragalus (Fabaceae) in the Lebanon biogeographical crossroad

The Lebanese mountain range is an important zone of plant species richness and endemism where the genus Astragalus constitutes a principal component of plant biodiversity. Most of endemic Astragalus taxa, living in mountains and arid zones of Mounts Lebanon and anti-Lebanon, are characterized by a cushion, spiny vegetative form, named “tragacanthic”, which is a remarkable example of vegetative convergence evolution. Because of determination difficulties, taxonomic uncertainties, and discrepancy in the number of taxa listed according to authors, new data are hardly needed to improve systematics of Astragalus and to investigate the role of the Lebanese mountain range as refugia of biodiversity. Before this study only two values on the genome size of Astragalus were reported in the literature and no previous molecular studies had been carried out on Astragalus genus in Lebanon. We examined the utility of rDNA ITS molecular markers to distinguish Astragalus species of Lebanese mountain range and the variation range of their genome size. The main results revealed a striking diversity in Lebanese Astragalus species with the emphasis of a huge variation of genome sizes, an important inter-specific chromosome polymorphism and the existence of a high phylogenetic diversity. The strict endemic species of the Lebanese mountains are positioned throughout the phylogeny. These results confirm that the Lebanon and anti-Lebanon mounts constitute a third diversity center for Astragalus and that high altitude areas are important refugia of plant biodiversity despite centuries of exploitation by humans.

Conservation unit allows assessing vulnerability and setting conservation priorities for a Mediterranean endemic plant within the context of extreme urbanization

Current biodiversity patterns are a temporary state in a continuum of ecological and evolutionary changes. Conservation policies must incorporate this dynamic to ensure the long-term conservation of biodiversity which is particularly challenging in a context of extreme urbanization. An original approach, rarely used for plant conservation, is to define conservation units to set conservation priorities within species by combining ecological and evolutionary divergences. In the Maritime Alps (southern France), the ecological and evolutionary divergences between the populations of Acis nicaeensis has allowed us the determination of conservation units of this endemic plant threatened by severe urbanization and land-use changes. Phylogeographical data (cpDNA haplotype) were considered as a proxy for evolutionary legacy, and ecological data (multivariate analysis of habitat) were used as a proxy for ecological distinctiveness. Our goal was to explore the potential of this approach to assess vulnerability and set conservation priorities for narrow endemic species in the context of conflict between biodiversity and human activities. The results highlight five different conservation units within A. nicaeensis distribution. Genetic and ecological divergences are present at fine-scale. This pattern is highly endangered by urbanisation. This study highlights the vulnerability of conservation units near the coast whose originality and restricted distribution call for rapid conservation management to avoid the loss of species evolutionary and ecological distinctiveness.

Analyse floristique et phytogéographique d'une région de l'Atlas saharien constantinois, les gorges du Ghouffi (Algérie)

Abstract The Gorges of Ghouffi (constantinois Saharan Atlas, Algeria) is a canyon with a depth of 200 m. Four dominant formations vegetation are highlighted in the part of the « balconies of Ghouffi »: the formations with Juniperus phoenicea, Artemisia herba-alba, Stipa tenacissima and the oasian ecosystem. This contribution aims to improve knowledge about the floral diversity of this site to promote its classification in protected area. This work will focus on the systematic study of flora, phytogeographical and biological significance of the flora of this region. A characterization of pharmaceutical plant species interests and values is also addressed. With a rate of endemism plant equal to 17%, the bio- geographic originality of this area is emphasized.

Acacia tortilis var. raddiana communities in the northwestern Algerian Sahara

Abstract The aim of this work is the phytoecological study of the Acacia tortilis var. raddiana desert savanna in the northwestern Algerian Sahara. Sixty-seven relevés were collected for this habitat from an area extending from the northern boundary of Béchar to the southern part of Kerzaz, a latitudinal gradient of 250 km. A detrended correspondence analysis identified two communities represented by 35 and 32 relevés. Canonical correspondence analysis highlighted the topography and the nature of the substratum as the main environmental factors explaining the distribution of the two groups. The most frequent community corresponded to the Acacia tortilis var. raddiana, Panicum turgidum and Foleyola billotii association Quézel 1965. It is associated with large wadi-beds and alluvial plains. This association presents two facies: a saxicolous one characterized by Farsetia occidentalis and Trichodesma calcaratum and a sandy facies with Kickxia aegyptiaca and Brocchia cinerea. The second community corresponds to the Acacia tortilis var. raddiana and Rhus tripartita association Quézel 1965, typical of narrow wadi-beds with rocky substrates. The floristic composition reveals fewer taxa of tropical origin and a reduced list of characteristic species is proposed. Details of the range of the two syntaxa identified are provided. They are compared with the other Acacia tortilis var. raddiana associations described for the Algerian central Sahara.