Diversity of phytophagous beetles (Coleoptera: Chrysomeloidea, Curculionoidea) in steppe communities in the forest-steppe of the High Trans-Volga region

A total of 551 species from 10 families of phytophagous beetles (superfamilies Chrysomeloidea and Curculionoidea) have been recorded in the steppe communities of the High Trans-Volga forest-steppe zone, 62% of which belong to the steppe landscape-geographic complex. The vast majority of the species belong to three families: Curculionidae (254 species; 46%), Chrysomelidae (186 species; 34%), and Apionidae (51 species; 9%). The regional steppe fauna has a complex arealogical structure combining the Western Scythian and Sarmatian elements, as well as relict species of the Angarian origin and some Eastern European ones. The highest diversity of phytophagous beetles is observed in the zonal meadow steppe communities (299 species; 54%). The most specific are the petrophilous steppe complexes which also include the greatest number of relict forms. Xerophilous Kazakhstan- Turanian species are mostly concentrated in the saline steppe communities of the southernmost forest-steppe zone. The species diversity is also high (249 species) in the open ruderal communities dominated by species characteristic of the pioneer stages of the steppe successions. Some steppe reservations include over 50% of the entire regional fauna of phytophagous beetles. The species diversity in the steppe localities decreases northward due to a gradual decrease in the number and proportion of the Scythian species: from 55% in the middle of the foreststeppe zone to 36% near its northern boundary. The species diversity of the slope communities in the forest-steppe zone is at least not lower than that in the similar areas of the steppe zone. The ratio of the number of Curculionoidea species to that of plant species is very high, reaching about 3: 4 in the model steppe localities of the High Trans-Volga forest-steppes, as compared to 1: 2 in the zonal steppe communities (according to the published data). The data considered confirm the significance of the forest-steppe zone as an important biodiversity center in the East European Plain and as a reservation of relicts of different origins.