Format: ORAL

Frdric Mdail frederic.medail@imbe.fr

Aix Marseille University, Mediterranean Institute of Biodiversity and Ecology (IMBE), Aix-en-Provence, Franc

This study aims to show the importance of small islands and islets (ie territories 1000 ha) of the Mediterranean Basin hotspot, including those of the Mediterranean and Macaronesian biogeographic regions, from the point of view of their plant biodiversity and their role in the conservation of coastal ecosystems. In the Mediterranean region, there are numerous islands ( 11,000) including a high diversity in term of plant species and of ecosystems types. These patterns can be explained by complex interactions between a highly heterogeneous historical biogeography and ecological processes. Furthermore, most of the ups and downs of this biodiversity were closely linked with human pressures which have changed many times through the long socio-ecological history of these island landscapes since the Neolithic period. In the Macaronesian region, small islands and islets (named PIMAs, by Mdail et al.,in prep.) are less numerous (n = 430). Islets with a surface area of less than 1 ha are predominant (88% of the whole PIMAs, i.e. 377 islets), and only 20 islands possess an area comprised between 11 and 1000 ha. These oceanic small islands are characterized by an exceptionally high richness of endemic taxa and constitute outstanding refugia for rare and threatened plant species. These PIMAs are nevertheless impacted by a diversity of human-related threats, notably the presence of invasive alien species, tourist pressure, or overgrazing. The level of knowledge of biodiversity is heterogeneous between the archipelagos and PIMAs are often neglected in conservation policies. If small islands and islets of the Mediterranean and Macaronesian regions have been neglected for a long period,current researches point out their disproportionate role to preserve coastal biodiversity (from genes to landscape). With regards to the biome crisis, they constitute key ecological systems and current refugia to ensure the long-term preservation of this highly threatened biodiversity.