Although it is well established that butterfly richness is affected by climate and human factors (e.g. habitat disturbance and degradation) at different spatial scales, the drivers behind these changes vary greatly according to the geographical region and the ecology of the species concerned. It is essential that this variation be understood if trends in diversity are to be predicted with any degree of confidence under a scenario of global change. Here we examine patterns of butterfly species richness among groups differing in degree of habitat specialization, diet breadth and mobility in the north‐west Mediterranean Basin, a European hotspot for this taxon. We analyze a large number of butterfly communities and take into consideration the main potential drivers, that include climatic, geographic and resource variables, landscape structure and human environmental impact at different spatial scales. Our study shows that both climatic and anthropogenic factors play an important role in determining butterfly species richness in the north‐west Mediterranean Basin, but that their relative impact differs between specialist and generalist groups. At lower altitudes, water availability, a product of the interplay between temperature and rainfall, and negative effects of temperature appear as the most determinant factors. Maximum diversity was observed at mid‐altitudes, which reveals the importance from a conservation point of view of Mediterranean mountain ranges. The results suggest serious population declines in specialist species restricted to mountain areas as a result of climate warming in combination with habitat loss caused by the abandonment of grazing and mowing. They also suggest negative trends for generalist species due to an increase in aridity in combination with an increase in intensification of human land use in lowland areas. Such synergies are expected to lead to rapid declines in Mediterranean butterfly populations in the coming years, thereby posing a severe threat for the conservation of European biodiversity.

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A total of 13 026 fishes belonging to 82 species and 43 famllies were collected in a continuous transect between depths of 200 and 1800 m south of the Baleanc Islands (Algerian basin, western Mediterranean). The analysis of 32 bottom trawls showed the existence of 4 groups associated with the upper slope (groups 1 and 2, from 200 to 400 and 400 to 800 m, respectivelv), middle slope (group 3, from 800 to 1400 m) and lower slope (group 4, below a depth of 1400 m) Thc differcnces in the mean values of the ecological parameters species richness, abundance, biomass and mean fish weight were also indicative of distinctive characteristics between these fish assemblages. Species richness decreased significantly with depth. The highest values of diversity corresponded to the samples from group 2. Biomass did not show any specific trend throughout the whole bathymetric range. Mean fish weight show 2 different trends along the continental slope: a bigger-deeper phenomenon at the upper 1000 to 1200 m depth. and a smaller-deeper phenomenon below this depth. Our results are compared with those obtained in the north Atlantic basin and in the western Mediterranean (Balearic basin), and the main factol-s affecting these deep-sea fish assemblages are discussed.

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