Résumé
In southern Europe, an intensive agricultural abandonment occurs for more than a century. This change in land use concerns both farming and breeding and induces a large-scale expansion of forest habitats. In the Mediterranean region, which is a centre of endemism and species richness for many groups, a large amount of biodiversity is related to ancient agricultural practices. This current abandonment could consequently induce a drastic flora and fauna impoverishment. This study attempts to identify the consequences of the widespread Mediterranean forest expansion on dung beetle assemblages. Dung beetle assemblages were monitored monthly with dung-baited pitfall trapping in four Mediterranean sites from 250 to 2030 m in elevation. At each site, different grazed habitats (grassland, forest and shrubland or wooded grassland) were sampled during the most seasonally active period. In total, 61,645 specimens consisting of 70 species, namely 65 Scarabaeidae (42 Aphodiinae, 23 Scarabaeinae) and 5 Geotrupidae. Sixty-four out of the 70 sampled species (91.43%) were widely distributed in the Palaearctic region. A drastic loss in species richness consecutive to the replacement of grassland by forest was observed all along the elevation gradient: 63 species recorded in grassland habitat versus 60 and 45 species in shrubland and forest, respectively. There was often a loss in species richness according to elevation: 45 versus 30 species in low and high elevation, respectively. For Aphodiinae, the extension of forest also induced a shift in distribution across elevation. This important biodiversity loss that is mainly concerned with lowland thermophilous species was accompanied by crucial changes in the structure of assemblages. The measurement of alpha and beta-diversity in different habitats as well as between habitats across an elevation gradient is essential to our understanding of which habitats are required to best conserve biodiversity. Alpha diversity decreased from grassland to shrubland to forest. Intra-habitat alpha and beta-diversity decreased with elevation. Whereas, inter-habitat beta-diversity (spatial turnover) increased from grassland to shrubland and then to forest regardless of elevation. The contrarily, intra-site beta-diversity increased with elevation. Thus, at the regional scale, the spatial turnover decreased with elevation and increased with the vegetation cover. So, the composition and structure of dung beetle assemblages were affected by vegetation cover, which causes a decreasing abundance and species richness and could result in a drastic loss of dung beetles biodiversity in southern Europe.