Hotspots within hotspots: insight of biogeographical conservation strategies in a transboundary territory (South-western Alps). Mission Bodiversity: Choosing New Paths for Conservation

Conservation challenges are particularly important within regional hotspots of biodiversity. This is the case of the South-western Alps (France – Italy) situated at the interface of Alpine and Mediterranean biomes. Thus, one aim is to provide practical and biogeographical analysis, allowing the identification of small key areas, where protected areas can prevent biodiversity loss concretely. To investigate how protected areas are able to be conservation tools for patrimonial species diversity, we used (i) a fine scale analysis (grid of 15 km²), (ii) a representative sample of the vascular plants diversity of the territory reflecting originality, rarity and threat, and (iii) three networks of protected areas, classified according to the efficiency of the protection they provide. First, we performed the spatial species richness patterns of two groups of patrimonial plants (endemic and threatened species). 876 species (i.e. 25 % of the flora) have been considered and more than 500 000 occurrences were used in the dataset. Two indices of species richness were computed and a restricted part of the territory (the top 5% richest cells) was considered as “hotspots” of diversity.Spatial congruencies of diversity patterns with protection networks were then evaluated. Our results show that protected areas well includes hotspots of diversity for the two groups considered (about 80%). The good comprehensive coverage of protected areas, thanks to the strong contribution of Natura 2000 network, hides large gaps for the strong protection network (IUCN categories of protected areas I to IV). We identified unprotected areas, mostly in the periphery of protected areas, which have remarkably high conservation values. The weak spatial congruence between endemic and threatened hotspots identified highlights the necessity of implementing multiple strategies and scales to answer complementary objectives in order to improve the expansion of the global protected-area network.