Abstract.-In the context of plant species rarity in mediterranean ecosystems, this study aims to precise the autoecology of the local annual endemic plant, Arenaria provincialis (Caryophyllaceae), by quantifying habitat and vegetation characteristics, and demographic parameters. Its populations are surprisingly scattered along a wide altitudinal and topological range, but over small geographical distances. This implies an important habitat differentiation from the thermophilous dry coast to the colder supra-mediterranean summits in open limestone rocky habitats such as steep screes, ledges, cracks or crests. Among the 163 plant species identified in presence of A. provincialis within 100 m 2 area, 92% belong to the stress Grime pole, highlighting the stressful conditions within the different habitats caused by drought, strong wind, and high thermic contrasts. Demographical surveys reveal strong spatial and temporal fluctuations.Key words : annual plant species -autoecology -rocky habitats -endemismdemography.Résumé.-Dans le contexte de la rareté des espèces végétales dans les éco-systèmes méditerranéens, l'objectif de cette étude consiste à préciser l'autoé-cologie d'une plante annuelle endémique, Arenaria provincialis (Caryophyllaceae), en quantifiant les caractéristiques des habitats et de la végé-tation associée ainsi que les paramètres démographiques. Ses populations s'étalent, de manière surprenante, le long d'un large gradient altitudinal, mais sur de petites distances géographiques. Ceci implique une importante différencia-tion des habitats, du littoral sec thermophile aux sommets froids supraméditer-ranéens, au sein d'habitats ouverts, calcaires rocheux tels que les éboulis pentus, les corniches, les anfractuosités des rochers ou les crêtes. Parmi les 163 espèces végétales associées à A. provincialis, sur des surfaces de 100 m 2 , 92% appartiennent au pôle stress des stratégies écologiques de Grime, ce qui met en exergue les conditions stressantes au sein des différents habitats du fait de la sècheresse, de vents forts et d'importants contrastes de température. Les suivis démographiques révèlent de fortes fluctuations spatiales et temporelles.Mots clés : autoécologie -démographie -endémisme -milieux rocheux -plante annuelle.

Abstract.-The last IUCN evaluation of the sandwort of Marseilles (Arenaria provincialis Chater & Hallyday) places this species in the « Rare » category according to old categories dating back from before 1994. A better knowledge about its natural history now allows us to revaluate its status. This winter therophyte, endemic to Provence, protected by national and international texts, lives in calcareous screes and rocks. After assessing its geographic area and the total number of mature individuals, none of the IUCN criteria version 3.1 (2001) is completely applicable. Nevertheless its extent of occurrence and area of occupancy are limited, and many threats could have a negative effect on its habitat. Thus, we propose the new status "Near threatened" (NT), more or less equivalent to the ancient category « Rare » (R). We therefore strongly suggest a regular revaluation of its status, increasing knowledge, experimental restoration and a global management plan to avoid a deterioration risk. Key words

The Armeria populations (Plumbaginaceae) scattered along the south-eastern French coastline are small and often endangered by habitat destruction. Because their taxonomic status remains unclear, we conducted a molecular and phenetic analysis to test for the existence of different taxa and to set conservation priorities. Multivariate analysis of morphometric data demonstrated that the majority of coastal populations are similar to inland populations of Armeria arenaria subsp. bupleuroides. However, discriminant analysis isolated two distinct populations. One of these has a morphology intermediate between the narrow endemic Armeria belgenciensis and A. arenaria subsp. bupleuroides. However, rDNA internal transcribed spacer (ITS) sequences display no fixed variation, even between highly remote populations. We discuss these results in the light of recurrent hybridization in Armeria, and propose the description of two new subspecies of Armeria arenaria (subsp. pradetensis and subsp. peirescii) located in the Var department.

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