The role of nature reserves in preserving saproxylic biodiversity: using longhorn beetles (Coleoptera: Cerambycidae) as bioindicators

The potential of forest nature reserves as refuges for biodiversity seems to be overlooked probably due to their small size. These, however, may constitute important safe havens for saproxylic organisms since forest reserves are relatively numerous in Europe. Saproxylic beetles are among the key groups for the assessment of biodiversity in forest habitats and longhorn beetles may play an important role in bioindication as they are ecologically associated with various micro-habitats and considered a very heterogeneous family of insects. To study the role of forest reserves as important habitats for saproxylic beetles, we compared cerambycid assemblages in corresponding pairs of sites (nature reserves and managed stands) in a forest region under high anthropogenic pressure (Upper Silesia, Poland, Central Europe). Moreover, we also intended to assess the role played by these beetles as bioindicators in the different forest types from this area. According to the obtained diversity index values, the most valuable stands are located in nature reserves, whilst sites with the lowest value included managed forests together with two homogeneous and relatively recently established nature reserves. Our analyses demonstrated a positive correlation between deadwood volume and biodiversity, for both species richness and abundance. Our results indicate that the decisive factor is the type of a given habitat, whose characteristics can be mainly influenced/determined by forest management. The potential role of longhorn beetles as bioindicators is highlighted and the effectiveness of using traps in this family, as well as general issues regarding the use of non-selective lethal traps in the study of single invertebrate groups in protected areas are discussed.