Landscape differentiation of butterfly assemblages (Lepidoptera, Hesperioidea et Papilionoidea) in middle taiga of Karelia

Butterfly assemblages were studied in agricultural and forest landscapes for 4 seasons. 3832 species of 50 types were observed during 1554 transect counts at 111 sites. The similarity in the list of observed species amounted to 90 %. The differences are attributed to single findings of migrants such as Pontia edusa, Colias hyale, Issoria lathonia, and localization of populations of Pyrgus alveus, Aricia nicias and Boloria freija. Landscape heterogeneity is most clearly displayed in the ratio between relative density and occurrence of species. Essential differences were found in the structure of population. Pieris napi, Nymphalis urticae and Thimelicus lineola prevail in agricultural area. Such forms as Callophrys rubi, Brenthis ino, and Erebia ligea dominated in forest environment. Together with Gonepteryx rhamni, which dominated in both cases, the total proportion in studied samples was 29 and 42 %, respectively. The landscape differentiation is determined by the ratio of suitable habitats. Comparisons of species’ richness, population density, and а-diversity show that butterfly assemblages of similar sites vary insignificantly. Clustering of assemblages by component analysis (PCA) indicated three main trends in variations of butterfly abundance: the affinity of species to either peatlands, meadows or forest environment. The obtained results speak of the role played by the landscape structure for population development and support our conclusion that butterfly assemblages in middle taiga are characterized by high stability. The stability, first of all, is provided by habitat selection of different species.