Distribution of entomopathogenic nematodes in the Swiss Alps

Abstract

A total of 473 soil samples taken from alpine regions in Switzerland was analysed for the presence of rhabditid entomopathogenic nematodes. These parasites were found in 27% of the samples at altitudes between 490 and 2530 m asl. The recovered nematode isolates fall into six species: Steinernema affinis, S. feltiae, S. intermedia, S. kraussei, Steinernema sp. (a species close to S. intermedia), and Heterorhabditis sp. (North-West European Group). The distribution of these species is discussed in relation to altitude, vegetation, orientation, soil characteristics (i.e. pH, sand content, content of organic matter), and potential host species. Steinernema kraussei was the most commonly encountered species, usually occurring in acidic soils rich in organic matter. Steinernema feltiae, the second most prevalent species, was rather confined to grassland habitats of the lower Alps and the Swiss Plateau. Similarly, the other species were usually found in grassland, but were too rare to draw conclusions about their ecological requirements.