Influence of individual variation in the trophic spectra of Pterostichus melanarius (Coleoptera, Carabidae) on the adaptation possibilities of its population

Abstract

Data on the selection of food items by Pterostichus melanarius (Illiger, 1798) obtained under laboratory conditions are discussed. An average of 40 prey species was offered to each individual during each separate experiment. Individual P. melanarius in forest ecosystems in the steppe zone of Ukraine eat zoophages of the I, II, and III orders, phytosaprophages and phytophages. Most ground beetle individuals prefer phytophages (up to 85%) in laboratory experiments, but certain individuals eat mostly zoophages of the II order, which make up more than 90% in their ration. The trophic preferences of P. melanarius can be classified into 5 clusters. In each of the clusters, there are representatives of 3 or 4 orders that belong to different trophic groups. One third of P. melanarius individuals feed on the representatives of the Lumbricomorpha order, one quarter on prey items from the Coleoptera and Isopoda orders. In 30% of the individuals studied it is difficult to single out a dominant taxonomic group in the feeding spectrum. During our laboratory experiments half the P. melanarius individuals selected prey items with a body mass of less than their own weight, others selected prey items that exceeded their own size. No distinct dependence exists between the individual variation in the trophic spectra of P. melanarius and their morphometric characteristics. Thus, P. melanarius is able to influence differentially various trophic, size-and-weight and taxonomic groups of invertebrate animals, producing a significant effect on the structure of invertebrate animal communities of the leaf litter.