Ground beetles (Coleoptera, Carabidae) in a fragmented landscape : woodland patches along a highway

Roads are widespread and increasing features of most landscapes. Such linear elements bisect landscapes, where as a result more and smaller habitat patches with reduced connectivity and higher proportions of edge habitat are expected. These impacts can reduce the chance of survival of populations of individual species and can influence essential ecosystem processes due to isolation, having a strong negative effect on the ecological values of habitats. In the last decades, there has been growing concern about ecological effects of roads, and fragmentation of habitat is considered as the most detrimental effect. Nevertheless, the habitat elements for wildlife provided by roadsides could partially compensate these adverse effects. Although they are unlikely to fully substitute the original habitat, roadsides can provide resources that are rare or missing in the surrounding landscape. Belgium is one of the countries with densest infrastructure. In Wallonia, southern Belgium, most of the present major roads are the result of an intensive development of infrastructure started at late 1960's. As a consequence several existing woodlands were bisected, and newly established woodland patches emerged, as part of road management in sites formerly committed to agricultural practices. Along E42 highway 30 woodland patches were surveyed and ground beetles (Coleoptera, Carabidae) were selected as indicators. We aimed to provide a broad characterisation of assemblages of both types of fragments, and to determine the factors shaping these assemblages, as well as the potential of these woodland patches as reservoirs of invertebrate diversity in a fragmented landscape with prevailing agricultural land use. The results of two years of sampling have revealed the different structure and composition of ground beetle assemblages supported by both types of patches. Effects as size, isolation and habitat quality of patches showed to be significant in shaping carabid assemblages. Although planted patches are unreachable and unsuitable to certain woodland species, they appear to play an important role as refuge for field-inhabiting carabids in the agricultural landscape. In formerly continuous patches characteristic species were predominantly woodland carabids, though it seems that those patches have already lost typical forest species of high conservation value. Integrating these patchy habitats to the network of nature reserves might maximise conservation of biodiversity in a region where few natural or seminatural habitats remain. Our results illustrate the usefulness of ground beetles as suitable indicators for comparative studies of recent and ancient woodland faunas, as well as for studies on impacts of habitat fragmentation.Doctorat en sciences (sciences biologiques) (BIOL 3)--UCL, 200