Conservation value of semi-open habitats for ground beetles (Coleoptera: Carabidae, Cicindelidae) in Central Europe

Abstract

AbstractReintroduction of grazing to counteract insect decline will lead to an increase of semi-open habitats. Semi-open habitats are highly heterogeneous, consisting of a mosaic of patches of trees or shrubs embedded in a matrix dominated by dwarf shrubs or grasses. Despite a lack of evidence, structural heterogeneity is expected to allow many species to co-occur, making semi-open habitats appear highly valuable for invertebrate conservation. We studied ground beetles in eight sites in two landscapes of Central Europe each encompassing semi-open, open, and forest habitats. Rapid response to environmental change and limited dispersal abilities make ground beetles an excellent model taxon to evaluate the effectiveness of such conservations measures. In both studied landscapes, ground beetle assemblages in semi-open habitats tended to be distinct and intermediate between those from the forest and open habitats. Species richness and functional diversity in semi-open habitats were similar to open habitats at site level. The majority of species entered the semi-open habitats, except for most threatened species, yet, few species were exclusively associated with semi-open habitats. We conclude that the continuous presence of many species in semi-open habitats likely results from mass effects rather than habitat heterogeneity per se. Our findings underline the conservation value of the existing forest, heathland, and grassland habitats over semi-open habitats which can, however, function as dispersal habitats and increase landscape connectivity. Strategies aiming at promoting semi-open habitats to counteract insect decline should target enhancing connectivity rather than the creation of habitats only.