The Silene mollissima (L.) Pers. aggregate is part of section Siphonomorpha Otth. and currently comprises 11 narrow endemic species of the Western Mediterranean Basin. Three of these taxa (S. velutina Pourr. ex Loisel, S. ichnusae Brullo, De Marco & De Marco f., and S. badaroi Breistr.) have a distribution range centred in the northern Tyrrhenian area and occurring in coastal habitats. Inter- and intra-specific variability in the responses to light, constant (5–25 °C) and alternating temperatures (25/10 °C), salt (NaCl, 0–600 mmol/L), and levels of nitrate (KNO3, 20 mmol/L) under salt stress, as well as recovery of seed germination were evaluated for these species to more effectively support their in-situ and ex-situ conservation. Our results highlighted that the seeds of these three taxa were nondormant, and that light significantly improved their rate of germination, which was higher (>80%) at low temperatures (5–15 °C) and under the alternating temperature regime (25/10 °C), but decreased significantly at the highest temperature tested (25 °C). Seeds from Silene velutina and S. ichnusae germinated in up to 300 mmol/L NaCl, and S. badaroi germinated in up to 100 mmol/L. For all of the species except S. badaroi, salt did not affect seed viability, and recovery germination did not decrease with increasing salinity and temperature. Interpopulation variability, both in salt tolerance and recovery germination, was detected for S. velutina. The addition of KNO3 did not affect germination or recovery germination under salt conditions. The lack of effect from KNO3 suggests that nutrient availability is not a requirement for seed germination in these species. Our results show that all species experience an optimum period of germination during autumn–winter, which is when water availability is highest and soil salinity levels are minimal because of the Mediterranean rainfalls, but seeds from S. velutina and S. ichnusae will germinate up until spring.

This article provides a comparison of the vascular alien flora of Sardinia (Italy) and that of Corsica (France), both territories belonging to the Western Mediterranean biogeographic subregion. The study has recorded 598 (90 doubtful) alien taxa in Sardinia (18% of the total flora) while 553 (87 doubtful) in Corsica (17%); six are new report to Sardinia and 27 to Corsica. A total of 234 taxa are common to both islands. Neophytes are 344 taxa (68% of the total) in Sardinia and 399 taxa (73%) in Corsica. The invasive component includes 64 taxa in Sardinia (13% of the alien flora) and 99 taxa (21%) in Corsica, 33 of them common to both territories. The total 740 alien taxa of Sardinia and Corsica are included in 93 families; being Fabaceae the richest. The comparison of the biological spectrum reveals that phanerophytes (202 taxa, 40%) are the most represented in Sardinia and therophytes (149 taxa, 32%) in Corsica. A study of the geographical origin shows supremacy of the American element in Sardinia (170 taxa, 34%) and in Corsica (136 taxa, 29%). The majority of taxa arrived as a result of intentional human introductions, mainly for ornamental use (247 taxa, 49% in Sardinia; 208 taxa, 45% in Corsica). Seminatural, agricultural and synanthropic are the most occupied habitats. These data show the need for joint action to stem the increasingly worrying phenomenon of the alien flora in order to reduce the negative effects on natural habitats and native flora.

Rouya polygama (Apiaceae) is an endangered Mediterranean species of great phytogeographical and ecological interest, growing on coastal sandy dunes. Intraspecific variability in the responses to constant temperatures (5-25°C) and an alternating temperature regime (25/10°C), salt stress (0-600A mM NaCl) and recovery of seed germination was evaluated among six populations from Sardinia and Corsica. Seeds were non-dormant and germination percentages ranged from 10 to 83%, depending on temperature and population. Differences in germination percentages were mainly due to different seed mortality among seed lots. R. polygama seeds germinated in salt concentrations up to 200A mM NaCl, whereas higher salt concentrations totally inhibited germination. Salt affected seed viability, and the recovery response decreased with increasing salinity and temperature. Inter-population variability and different sensitivity to NaCl in seed germination were detected. Our results are consistent with field germination in a period from autumn to spring, when water is available in the soil and temperatures are not prohibitive for seedling establishment, representing an advantageous ecological adaptation for seedling establishment to the unpredictable Mediterranean rainfall pattern. Further studies on R. polygama are needed to investigate germination requirements at temperatures higher than 25°C and its germination in the field, and to clarify genetic inter-population variability, considering a higher number of populations and possibly extending to North African populations

This study reveals contrasted dynamics of orchid communities between local and regional scales in Corsica. Although high turnover in communities was found at the local scale, regional species richness was maintained despite major land-use changes. Conserving landscape mosaics could provide locally suitable habitats for orchids of different ecologies to maintain diversity at larger spatial scales.

Plant leaves host species rich communities of foliar endophytic fungi (FEF). Compared to the other compartments of the plant microbiome, FEF diversity is poorly known. Here we document the communities of FEF associated with the endemic Corsican pine Pinus nigra subsp. laricio at three sites across its natural range and examine the effect of forest site, tree age and light exposure on FEF composition. Metabarcoding using next-generation sequencing provided 8,243,608 Ascomycota ITS2 sequences clustered into 642 FEF operational taxonomic units (OTUs). FEF communities did not differ in species richness across sites and tree cohorts, but differed in composition among forest patches and according to tree age. FEF community composition did not correlate with needle location (shade vs full light). Results are robust against the various options of the bioinformatic pipeline specifically developed. This study provides the first picture of FEF diversity in a Mediterranean island and underlines the complementarity of forest massifs for fungal conservation.

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.

Philaenus spumarius (Ps) is considered the main insect vector of the bacterium Xylella fastidiosa (Xf) in Europe. As such, it is a key actor of the Xf pathosystem on which surveillance and management strategies could be implemented. Although research effort has increased in the past years, the ecological factors shaping Ps abundance and distribution across landscapes are still poorly known in most regions of Europe. We selected 64 plots of 500m2 in Corsican semi-natural habitats in which we sampled nymphs and adults of Ps during three years. While local or surrounding vegetation structure (low or high scrubland) had little effect on Ps abundance, we highlighted a positive relationship between Ps abundance and the density of Cistus monspeliensis in the plots. We also found larger populations of Ps in cooler and moister plots. The pattern of host association highlighted here is unique, which calls for more studies on the ecology of Ps in Europe, to help designing surveillance and management strategy for Xf.

En France, la carte géographique d’état-major, levée de 1818 à 1866, couvre l’ensemble du pays en 273 feuilles. C’est sous Louis XVIII que la réalisation de cet immense chantier a commencé, en 1817, pour répondre au départ à des besoins civils et militaires. La Corse a été la dernière région française cartographiée (entre 1864 et 1866) ; elle est représentée par 22 feuilles de minutes éditées au 1 : 40 000. La reproduction du relief est la grande nouveauté apportée par ces cartes. Mais elles sont surtout une formidable source de données historiques spatialisées qui nous indique l’occupation du sol par les cultures, les vignes, les marais, les maquis, les forêts ou encore les habitations. À cette époque, le territoire était très ouvert avec 83 % de la surface non boisée où les activités humaines, notamment pastorales, marquaient fortement le paysage (60 % du territoire en pacage ou en parcours). 20 % de la Corse était cultivée et il y avait déjà plus de 7 000 ha de vignes. Concernant la part de la forêt, il y a 150 ans, elle représentait près de 154 000 ha, alors qu’aujourd’hui on l’estime à plus de 500 000 ha (IGN 2013). C’est-à-dire qu’elle a été multipliée par un coefficient 3 pendant cette période. Calculée avec comme date de référence celle de la carte d’état-major, la part des forêts anciennes serait égale à 80 000 ha en Corse. Ce sont vraiment les essences de montagne qui ont gardé le plus longtemps un continuum de leur état boisé, avec les forêts de pin laricio (Pinus nigra subsp. laricio Maire) et de hêtre (Fagus sylvatica L.). A contrario, ce sont les suberaies (chênes-lièges, Quercus suber L.) qui ont payé le plus fort tribut au développement urbanistique et agricole du territoire. Une autre information intéressante que nous apportent les données de l’état-major, est la présence de forêts à l’étage subalpin (entre 1 600 et 2 100 m d’altitude) que l’on ne retrouve plus aujourd’hui. Cependant, depuis quelques décennies, on observe une remontée de quelques essences forestières comme le sorbier des oiseleurs (Sorbus aucuparia subsp. praemorsa (Guss) Nyman.) et l’érable sycomore (Acer pseudoplatanus L.) à ces altitudes, fortement liée à la déprise des territoires d’estives.