Populations of the specialist gall-forming fly, Urophora cardui (Diptera: Tephritidae), were studied at the western and eastern margins of its distribution. In western Europe U. cardui attacks the creeping thistle Cirsium arvense, whereas in eastern Europe, in the Ural mountains, it attacks Cirsium setosum, a taxon closely related to C. arvense. Gall densities are high in the Ural mountains and can be predicted by environmental variables. Compared to galls on C. arvense, those on C. setosum are on average larger. This indicates better performance of U. cardui on C. setosum in terms of cell numbers per gall. Despite the wide distribution of U. cardui, the dominant parasitoids are the same at the western and eastern ends of its distribution and the interactions between parasitoids and the host are similar. In general, we suggest that the synchronisation between the host plant species, the phytophage and the parasitoids is an important factor in the spatial ecology and evolution of this food web.
Mathematical modelling is shown as an efficient tool for studying the behaviour of reservoir ecosystems. Two mathematical models, namely ASTER and DYRESM-WQ and their characteristic features are described. The parameters of both models and their values used for simulation of reservoir Rimov are presented. Sensitivity analysis for both models was performed in the scope to demonstrate the sensitivity of simulation results to the parameter changes. The simulation results were compared to the measurements in situ with satisfying accuracy. The suitability of application of both models on the food web simulation of valley reservoirs is discussed. and Článek ukazuje matematické modelování jako účinný prostředek pro studium chování ekosystémů údolních nádrží. Popisuje dva matematické modely, a to ASTER a DYRESM-WQ, a jejich charakteristické rysy. Podrobně jsou ukázány parametry obou modelů a rovněž jejich hodnoty, jichž bylo použito k simulaci údolní nádrže Římov. Pomocí citlivostní analýzy byla zjištěna u obou modelů velikost odezvy systému na změny některých parametrů. Porovnání výsledků simulací s hodnotami naměřenými v nádrži ukazuje dostatečnou přesnost matematického modelování. V závěru je diskutována vhodnost použití matematického modelování pro simulaci potravního řetězce v údolních nádržích.
1) Alloxystinae are major secondary parasitoids of aphids, important in both their ecology and pest management. 2) Two radically differing views of alloxystine taxonomy exist in the literature, in one of which the group is very diverse, in the other it consists of a few variable species. 3) We sequenced a variable nuclear gene region (ITS2) for 28 specimens of a morphologically clearly defined group which, in one view belong to a single species and in the other to four species. We find that the four putative species each carry a different unique allele with no intraspecific variation. We show that the probability of the observed distribution of alleles under the assumption of a single interbreeding population is very small and we reject the view that all specimens belong to a single biological species. 4) We discuss the implications of our results for aphid - parasitoid community ecology and the biological control of aphids with parasitoids.