Die Regenwürmer Proctodrilus tuberculatus (Černosvitov, 1935) und Proctodrilus antipai (Michaelsen, 1891) als Indikatoren der fossilen Oberflächengliederung der Flussaue (Oligochaeta: Lumbricidae)

Abstract

Höser, N.: The earthworms Proctodrilus tuberculatus (Černosvitov, 1935) and Proctodrilus antipai (Michaelsen, 1891) as indicators of fossil surface structure in riverine floodplains (Oligochaeta: Lumbricidae). – Hercynia N.F. 41 (2008): 263 -272.In riverine floodplains of Central Germany, the distinct ecological vicariance of the earthworms Proctodrilus tuberculatus (Černosvitov, 1935) and P. antipai (Michaelsen, 1891) can be demonstrated. In general, in these floodplains the former species mainly prefers soils of a more terrestrial character (alluvial pararendzina, Vega), while the latter, by contrast, prefers soil associations of the alluvial gley type. P. tuberculatus inhabits the chiefly syngenetical (synsedimentary) types of soil of the partly layered alluvial sediments that are deposited close to the main channel on steep banks and in adjoining valley bottoms near the river, while P. antipai is restricted to epigenetically more developed soils of extremely fine particle size occurring at the floodplain edges farther from the river. Given these ties to particular biotopes, and the longevity of soil characteristics, the distribution of the two earthworm species in the floodplain cross-section reflects not only the present, but in some places also the past surface structure of the plain. Three examples are presented of how the presence of P. tuberculatus in the parts of the floodplain edge inhabited by P. antipai indicates fossil structures of a past floodplain surface: namely, P. tuberculatus as an indicator of a fossil secondary floodplain channel, of a fossil primary floodplain channel, and of a river course filled in by the action of natural floodplain dynamics. In the first two examples it can be shown that the soil profile, separated into two layers according to texture because of the different provenances of the substrate, is inhabited in one of its layers by P. tuberculatus and in the other by P. antipai, which is an illustration of ecological vicariance within the soil profile.