Investigation on competitors and predators of herbivorous aquatic Lepidoptera (Acentria ephemerella) on submersed macrophytes in a large prealpine lake

Abstract

Submersed macrophytes offer a large colonization area for many macroinvertebrates. Numerous studies investigated the interaction between plant species, growth and leaf form and the abundance and species composition of invertebrates (e.g. SOSZKA 1975, KORNIJOW & KAIRESALO 1992). Grazers and detrivores assist the plants by removing epiphyton and allowing more light to reach the photosynthetic tissue. Only recently has the paradigm that aquatic angiosperms are not subjected to a high degree of herbivory been challenged (LODGE 1991, NEWMAN 1991, KORNIJOW 1996, LODGE et al. 1998). A detailed study of the literature reveals that aquatic insects were frequently observed feeding on submersed macrophytes. For example, Acentria ephemerella, a true shredder–herbivore, was found associated with pondweeds and other macrophytes in several studies (BERG 1942, MULLER-LIEBENAU 1956, SOSZKA 1975). Acentria seems to prefer large lakes to small ponds as habitat (JOHNSON et al. 1998). Data on its abundance in different lakes range from a few dozen to many hundred species per square meter (SOSZKA 1975, HEDAL & SCHMIDT 1992, BANZIGER 2000, JOHNSON et al. 2001, GROSS et al. in prep.).