Katia Diadema

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.

Genomic DNA isolation and amplification from callus culture in succulent plants, Carpobrotus species (Aizoaceae)

Genomic DNA of high quality and quantity is needed to analyze genetic diversity with AFLP.Carpobrotus plant species, like most succulents, contain high amounts of polysaccharides and polyphenols, making PCR amplification difficult. Our protocol eliminates contaminants before DNA isolation by using leaf callus as plant material. This simple and inexpensive technique gives an average DNA yield of 1800 ng/g of callus and high reproducible profiles in AFLP. Our results indicate that no genetic variability is associated with callus culture conditions. This technique is suitable for studying genomic polymorphism in succulents and other plants when classic DNA extraction procedures fail.

Écologie et distribution de la Nivéole à longues feuilles (Acis longifolia = Leucojum longifolium), Alliaceae endémique de Corse

Abstract The aims of this study are to examine the distribution and the ecological requirements of Acis longifolia (J. Gay ex Salisb.) J. Gay ex M.J. Roem. (Alliaceae), a paleoendemic geophyte with a restricted distribution in Corsica. Among the 45 populations actually censused, most of them are located in the Cintu and the Rotundu sectors. Even if the center of the range of this snowflake remains the north-western part of the island, several populations were recently discovered in the periphery of the range, within the sectors of the Cap Corse, the San Petrone and the Incudine-Bavella. A. longifolia is found from the coast to 1500 m a.s.l. This plant has a strong ecological plasticity, but it is preferentially found on some humid and quite cool crevices of siliceous and shaded rocks located at low and medium altitudes. We considered that it is not directly threatened at present, but its small range requires an adequate survey, particularly for the low altitudinal populations which consist of a reduced number of plants.

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.

Écologie, distribution et morphologie comparées des nivéoles de Nice (Acis nicaeensis) et de Fabre (Acis fabrei), Alliaceae endémiques des Alpes maritimes et et de la Nesque (Vaucluse)

Abstract Acis nicaeensis and A. fabrei are two endemic geophytes from the Maritime Alps and the Vaucluse (Nesque basin) respectively. The aims of this study are to establish the distinctive morphological characters between the two snowflakes, to examine the chorology and the demography of the populations, in addition with the evaluation of their ecological requirements. Among the most discriminating characters, leaf width, stigma—anther separation, number of internal tepal veins and diameter of the epigynous disk are the most useful. Thirty—six existing populations have been censused for A. nicaeensis occuring in ecological conditions ranging from thermophilous mattoral to xerophilous grasslands with annual or perennial species. The four known populations of A. fabrei are found on rocky grasslands in clearings. The different factors threatening the two snowflakes are discussed.