Effects of cypermethrin on the taxonomic diversity of soil and litter invertebrates in the agrocoenoses of Lithuania

Abstract

We assessed the degree to which cypermethrin impacts the taxonomic diversity of non-target groups of soil and litter invertebrates in the agrocoenoses of Kėdainiai District, Lithuania. The studies were conducted in three agrosystems, two of which have been farmed conventionally, with the use of insecticides (cypermethrin), and one where no chemical means had been applied. It was the first time that a modern graphic analysis was conducted for the distribution of the invertebrates depending on their average body length and their total abundance in an agrocoenosis. By number of species and their abundance, the most diverse group in all the examined agrocoenoses was Coleoptera, with a significant dominance of Carabidae. The dominant species of invertebrates in the studied agrocoenoses were Nebria rufescens, Loricera pilicornis, Metallina lampros, Poecilus cupreus, P. versicolor, Pterostichus melanarius, Amara aenea, A. communis, A. convexiuscula, Calathus ambiguous, C. fuscipes, Anchomenus dorsalis, Harpalus griseus, H. rufipes, H. distinguendus, Coccinella septempunctata, Lasius niger, and Pardosa lugubris. The conventionally farmed agrocoenoses of rapeseed and wheat were characterized by impoverished taxonomic compositions, with prevalence of several eudominant and dominant species (Pterostichus melanarius, Poecilus versicolor, and Calathus fuscipes). The size structure was significantly uneven. Most of the species recorded in these plots were zoophages, represented by flying and non-flying forms. In the ecologically farmed wheat agrocoenosis, which had not been treated with insecticides, we observed a relative eveness in the size structure, absence of eudominant species, and increase in the taxonomic diversity due to the distribution of non-target groups of arthropods that are more sensitive to cypermethrin (Porcellionidae, Lithobiidae, Tetrigidae, Acrididae, Coreidae, Lygaeidae, Cydnidae, Pentatomidae, Scarabaeidae, Elateridae, Chrysomelidae, Curculionidae, and Thomisidae). The percentages of zoophages declined, while the shares of phytophages and polyphages that are able to fly increased