The Endangered and Protected Carabus hungaricus Fabricius, 1792 (Coleoptera: Carabidae), in Bulgaria: Communities and Ecological Parameters of Populations from the Southernmost Refugium of the Eurasian Steppe Biome

This paper shows the results of a study on the ecological structure and spatial distribution of communities of the protected steppe ground beetle Carabus hungaricus Fabricius, 1792 (Coleoptera: Carabidae), in Bulgaria. It also points some phenological data and details about the species activity. In the period May 2021&ndash:December 2023, we explored 42 sample plots in xerophytic landscapes in central&ndash:western Bulgaria, representing the southernmost limits of the steppe fauna in Eurasia. With 252 pitfall traps, 69,903 effective trap-days were realised, and 15,333 carabid individuals from 184 species were identified. Carabus hungaricus was established in seven sites (frequency of occurrence, F = 16.7%), with a total of 198 specimens (1.3% of all carabids and almost 4% of the total dynamic density). In these seven sites, we found 57 species, mostly open habitat dwellers. The tribe Harpalini had 33% of the species. The most species-rich genera were Harpalus (13 species), Amara (8) and Carabus (6). Calathus distinguendus was superdominant with more than 71% of all carabid specimens. Euconstant species, collected in all seven sites (F = 100%), were Carabus coriaceus and Calathus distinguendus. The two classes of life forms had almost equal proportions, 28 (49.1%) Zoophagous and 29 (50.9%) Mixophytophagous species, which is extraordinary for Bulgaria, but typical for the Eurasian steppe zone. Macropterous beetles comprised 56% of the species and brachypterous were 25%, which is comparable only with typical montane habitats. Concerning humidity preferences, mesoxerophilous carabids predominated (25 species, 44%). In relation to its ground beetle fauna, the studied complex of habitats is quite remarkable for Bulgaria and appears to be stable and characteristic for the steppe biome.