ALTITUDINAL EFFECT ON SPECIES RICHNESS OF ONISCIDEA (CRUSTACEA, ISOPODA) ON 3 MOUNTAINS IN GREECE

The species richness of terrestrial isopods at several altitudinal zones on three mountains of continental Greece was investigated in Order to document the effect of elevation on this animal group. Species richness decreases with altitude, and at the same rate on all three mountains. The faunal similarity among altitudinal zones is inversely related to species density (total number of species present at each mountain), but is not related to latitude. Species density is constrained by environmental harshness, but is also influenced by historical factors. The faunal composition of the three mountains shows that these historical factors are crucial for the patterns of species distribution across elevational gradients found today, and are unified under the general concept of altitudinal effects.