Land-mollusc forest communities along an altitudinal transect in northern Italy

Abstract

While central and northern European land-mollusc forest communities have received considerable research effort, southern Europe has enjoyed much less attention. Despite the extent of Italian forests in terms of altitude and latitude, there has been only one previous quantitative study of their molluscan faunas. This paper describes the molluscan communities of six forest habitats in northern Italy along an altitudinal transect. Species richness had its highest values at low elevations, especially in maritime woodland and in riverine poplar woodland. Species abundance decreased from lowland to montane habitats, possibly as a consequence of a transition from eutrophic to oligotrophic habitats and from calcareous to acidic soils. Compared with the central and northern European forests, the Italian forests were poorer as far as species richness is concerned, but showed greater diversity among locations as the Jaccard presence/absence similarity index among habitats is equal or lower than 0.5. Considering abundances, all molluscan communities were significantly different in pairwise comparisons, with the single exception of the montane mixed-deciduous and beech forests. The low faunal similarity among sites and the high percentage of species found in only one habitat support the need for a network of diverse protected areas to preserve land-mollusc biodiversity.