Der Regenwurm Dendrobaena illyrica (Cognetti, 1906) an dernördlichen und nordwestlichen Grenze seiner Verbreitung (Oligochaeta: Lumbricidae)

. The earthworm Dendrobaena illyrica (Cognetti, 1906) on the northern and northwestern boundary of its distribution (Oligochaeta: Lumbricidae). The northern and northwestern boundary of the range of Dendrobaena illyrica (Cognetti, 1906), which runs through the eastern part of the edge of the Central European Uplands, is here more precisely determined on the basis of new localities. The species has been found in areas of the Böhmerwald/Bayerischer Wald, Oberpfälzer Wald, Fichtelgebirge, Vogtland, Erzgebirge and Elbsandsteingebirge. On the northern slope of the Erzgebirge, the range boundary corresponds to the 'flint line' marking the margin of the first Elsterian Cold Period glaciation. This earthworm species prefers forest soils formed on acidic magmatites and metamorphites as source rocks. We found both fully developed individuals of the species which reproduce sexually, and externally not fully developed adult individuals which we classed as the parthenogenetic form of the species. The distribution of both forms shows that parthenogenesis appears to occur geographically in D. illyrica, i.e. the sexual form predominates in optimal habitats near the core of the range, while the parthenogenetic form occurs in less favourable habitats and at the edges of the range.