TY  - JOUR
A1  - Hancock, Christine
A1  - Wäschke, Nicole
A1  - Schumacher, Uta
A1  - Linsenmair, Karl Eduard
A1  - Meiners, Torsten
A1  - Obermaier, Elisabeth
T1  - Fertilizer application decreases insect abundance on Plantago lanceolata - a large-scale experiment in three geographic regions
JF  - Arthropod-plant interactions : an international journal devoted to studies on interactions of insects, mites, and other arthropods with plants
N2  - Humans have substantially altered the nitrogen cycle of ecosystems through the application of agricultural fertilizer. Fertilization may not only affect plant species diversity, but also insect dynamics by altering plant nitrogen supplies. We investigated the effect of experimental fertilization on the vegetation, with the ribwort plantain as the focal plant, and on higher trophic levels on differently managed grasslands throughout Germany. Over a period of 2 years, we examined two specialist herbivores and their parasitoid on Plantago lanceolata L., and the composition and structure of the surrounding vegetation. Over 70 sites in three geographic regions, within the large-scale project "German Biodiversity Exploratories", were included in the study. The model system consisted of the host plant P. lanceolata L., the monophagous weevils Mecinus labilis Herbst and M. pascuorum Gyllenhal, and their parasitoid Mesopolobus incultus Walker. Fertilization decreased plant species richness and host plant abundance, whereas it enhanced the total vegetation growth. The increased size and heigher leaf nitrogen content did not improve herbivore performance. On the contrary, the abundance of the two herbivores was decreased by fertilization. The parasitoid depended on the abundance of one of its hosts, M. pascuorum (positively density-dependent). Reduced herbivore abundance due to fertilization might be explained by a lower abundance of the host plant, a lower stalk number, and by changed patterns of host localization within higher vegetation. Fertilization negatively affected the third trophic level by cascading up via host abundance. The relationships between fertilization, surrounding vegetation and the tritrophic system were measured throughout the three regions and over the 2-year period. Our findings present consequences of intensification for a plant-herbivore-parasitoid system, and may have significant implications for the conservation of multitrophic systems in managed grasslands.
KW  - Fertilization
KW  - Nitrogen
KW  - Tritrophic interaction
KW  - Plant species richness
KW  - Grassland management
KW  - Vegetation structure
Y1  - 2013
U6  - https://doi.org/10.1007/s11829-012-9237-9
SN  - 1872-8855
SN  - 1872-8847
VL  - 7
IS  - 2
SP  - 147
EP  - 158
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Heisswolf, Annette
A1  - Reichmann, Stefanie
A1  - Poethke, Hans Joachim
A1  - Schroeder, Boris
A1  - Obermaier, Elisabeth
T1  - Habitat quality matters for the distribution of an endangered leaf beetle and its egg parasitoid in a fragmented landscape
N2  - Fragmentation, deterioration, and loss of habitat patches threaten the survival of many insect species. Depending on their trophic level, species may be differently affected by these factors. However, studies investigating more than one trophic level on a landscape scale are still rare. In the present study we analyzed the effects of habitat size, isolation, and quality for the occurrence and population density of the endangered leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) and its egg parasitoid, the hymenopteran wasp Foersterella reptans Nees (Hymenoptera: Tetracampidae). C. canaliculata is strictly monophagous on meadow sage (Salvia pratensis), while F. reptans can also parasitize other hosts. Both size and isolation of habitat patches strongly determined the occurrence of the beetle. However, population density increased to a much greater extent with increasing host plant density ( = habitat quality) than with habitat size. The occurrence probability of the egg parasitoid increased with increasing population density of C. canaliculata. In conclusion, although maintaining large, well-connected patches with high host plant density is surely the major conservation goal for the specialized herbivore C. canaliculata, also small patches with high host plant densities can support viable populations and should thus be conserved. The less specialized parasitoid F. reptans is more likely to be found on patches with high beetle density, while patch size and isolation seem to be less important.
Y1  - 2009
UR  - http://www.springerlink.com/content/100177
U6  - https://doi.org/10.1007/s10841-008-9139-4
SN  - 1366-638X
ER  -