Restoration of semi-natural grasslands, a success for phytophagous beetles (Curculionidae)

Abstract: Semi-natural grasslands have rich plant and animal communities of high conservation value. The continuity and maintenance of these habitats depend on traditional agricultural methods, which nowadays give low economic output. Therefore biodiversity restoration measures in abandoned semi-natural grasslands have been implemented, which pay farmers for reestablishing and maintaining a semi-natural grassland biodiversity. Between 2000 and 2006 around 3500 ha of semi-natural grasslands were restored in Sweden. The main aim is to conserve the biodiversity, which is well known for its dependence on old agricultural lands. This study aimed to evaluate if these measures may also work successfully for the conservation of diversity of weevils, a phytophagous beetle family. This is a neglected taxon, when it comes to biodiversity assessments of restored grasslands in Europe, although many of them are grassland associated and red listed. Numerous weevils are dietary specialized or closely associated with certain plant genera or even single species, which are often habitat specialized as well. Our study was done by comparing the weevil species diversity and composition of abandoned, old restored, recently restored and continuously managed sites. In total 24 sites were included in the survey. The beetles were collected by sweep-netting. We found no differences in species richness between studied management categories. However the species composition of abandoned sites was significantly different compared to the restored and continuously managed sites. Moreover, the abandoned sites were dominated by polyphagous species whereas the restored and continuously managed sites contained more monophagous species. Our conclusion is that there is a restoration success targeting the phytophagous weevil community of semi-natural grasslands and this justifies the expenses connected with restoration measures.