Comparative analysis of fauna of the superfamily Curculionoidea (Coleoptera) in Protected Areas of the Orenburg Region, Russia

A detailed study of the species composition and structure of the fauna of taxonomically rich insect groups in Protected Areas is an important task, the results of which lay the foundation for long-term monitoring of natural ecosystems. A comparative analysis of the thoroughly studied local fauna of natural references allows us to make more in-depth solutions for a number of biogeographical problems. However, studies of Curculionoidea in large Protected Areas are devoted predominantly to compiling preliminary taxonomic lists without a comprehensive analysis of the fauna. This paper presents results of long-term research (2015–2021) in six similar in size Protected Areas of the Orenburg Region (Russia). In total, 510 species from four families of Curculionoidea were recorded (74% of the regional fauna species). Among them, 434 species were identified in five clusters of the Orenburg State Nature Reserve, which are located on the same meridional transect in the steppe zone of the South Urals (from Obshchy Syrt to the Turgay Plateau). The highest species richness of Curculionoidea is recorded in Protected Areas of the low mountains of the South Urals, namely in the forest-steppe Shaitan-Tau State Nature Reserve (296 species) and in the mountain-steppe clusters of the Orenburg State Nature Reserve: «Burtinskaya Steppe» (293 species) and «Aytuarskaya Steppe» (277 species). On the plain sites (Trans-Volga Region and Trans-Urals Region) of the Orenburg State Nature Reserve (Talovskaya Steppe and Aschisayskaya Steppe), where dry steppes and salt marshes on a gentle relief prevail with absence of forested areas, the species richness of Curculionoidea is 1.5–2.0 times lower (203 species and 149 species, respectively). Fundamental differences in the composition and structure of the fauna were found between the local fauna of the steppe zone (clusters of the Orenburg State Nature Reserve) and the mountain forest-steppe (Shaitan-Tau State Nature Reserve). In the fauna of the Shaitan-Tau State Nature Reserve, the proportion of species of the Central Palaearctic complex is two times lower (11%) comparing to the Orenburg State Nature Reserve (22%), with a much higher proportion of nemoral species (8.1% in the Shaitan-Tau State Nature Reserve against 3.9% in the Orenburg State Nature Reserve), as well as boreal and arctic-boreal species (4.5% in the Shaitan-Tau State Nature Reserve against 1.0% in the Orenburg State Nature Reserve). The lowest Jaccard similarity coefficient (KJ = 0.165) was between the fauna of the Shaitan-Tau State Nature Reserve and the cluster Aschisayskaya Steppe. The fauna of clusters of the Orenburg State Nature Reserve also have considerable differences (in particular, KJ between faunas of the cluster Burtinskaya Steppe and cluster Aytuarskaya Steppe is 0.56, and it is 0.27 between the fauna of the cluster Aytuarskaya Steppe and cluster Aschisayskaya Steppe). The conducted studies demonstrated spatial heterogeneity of the fauna of the Curculionoidea in the Orenburg Region. This is caused by the passage of a number of meridional and latitudinal biogeographic boundaries in the Orenburg Region, and it highlights a greater significance of the South Urals as a zoogeographic unit than it is usually considered.