Response of aculeate Hymenoptera to spatial features of an agricultural landscape

The impact of increasing distance to the edge of neighbouring land-use types on aculeate Hymenoptera was studied in the marginal region of the Lahn-Dill-Bergland (Central Hesse, Germany). Aculeate hymenoptera were sampled two weeks in August using coloured pan-traps that were located along four transects: A. abandoned land with increasing distance to grassland, B. arable land with increasing distance to grassland, C. grassland with increasing distance to abandoned land, and D. arable land with increasing distance to abandoned land. Each transect was completed by adding centres of adjacent sites with the respective interacting land-use type, i.e. centres of grassland to transects A and B as well as centres of abandoned land to transects C and D. mposition of aculeate Hymenoptera did not change along transects A and B, while several parameters of the community structure significantly changed along transects C and D. The species richness of wasps as well as the abundances of hypergaeic aculeate species and prey-specialised wasps was high on abandoned land and abruptly decreased in arable land without further change along the transect. Species richness of total Aculeata and wild bees as well as the abundance of total Aculeata, polylectic bees and endogaeic Aculeata gradually declined on grassland with increasing distance to abandoned land. Oligolectic bees did not respond to distance in any of the treatments investigated. It is concluded that the close association of both arable land and grassland to abandoned land covered with shrubs is a structural feature of cultural landscapes that positively affects the diversity and density of aculeate Hymenoptera. Conservation of areas covered by shrubs is thus an important management option.