Importance of marginal habitats for grassland diversity: fallows and overgrown tall-grass steppe as key habitats of endangered ground-beetle Carabus hungaricus

1. To facilitate effective conservation management of dry-grassland diversity we studied the habitat selection of Carabus hungaricus, the globally declining, highly endangered, dry-grassland specialist beetle listed in the EU Habitats Directive, and several co-occurring beetles at a pannonian dry-grassland fragment, the Pouzdrany steppe, SE Czech Republic. The beetles were sampled using 186 pitfall traps from March to November 2006. Number of C. hungaricus captures in each trap was related to vegetation and abiotic habitat characteristics; captures of all sampled beetles in each trap were related to each other. 2. We found that C. hungaricus prefers relatively humid patches of tall-grass steppe within the xeric grassland and tall-grass ruderal vegetation nearby. During the breeding period, females preferred drier and warmer sites than males. 3. Its potential competitors, i.e., Carabus spp., Calosoma spp. (Coleoptera: Carabidae), and other species of conservation interest, including Meloe spp. (Coleoptera: Meloidae), Dorcadion spp. (Coleoptera: Cerambycidae), were associated with vegetation avoided by C. hungaricus, such as short-grass and bare-soil patches and woody plants. 4. Vegetation structure within 2.5 m affected C. hungaricus captures more than on smaller and larger scales. Carabus hungaricus enters unfavoured non-forest habitats such as arable land, which allows it to spread into suitable habitats within agricultural landscapes. It strictly avoids closed forest; even narrow strips of forest thus likely act as migration barriers. 5. The preference of C. hungaricus for overgrown steppe and fallow land highlights that habitats often considered of low conservation value are important to sustain grassland biodiversity.