TY  - JOUR
A1  - Heisswolf, Annette
A1  - Reichmann, Stefanie
A1  - Poethke, Hans-Joachim
A1  - Schröder, 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.
KW  - Fragmentierung
KW  - Pflanzenfressende Insekten
KW  - Eiparasitismus
KW  - Metapopulation
KW  - Habitat fragmentation
KW  - herbivore
KW  - host plant density
KW  - metapopulation
KW  - multitrophic
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-47740
ER  - 
TY  - JOUR
A1  - Bonte, Dries
A1  - Hovestadt, Thomas
A1  - Poethke, Hans-Joachim
T1  - Evolution of dispersal polymorphism and local adaptation of dispersal distance in spatially structured landscapes
N2  - Many organisms show polymorphism in dispersal distance strategies. This variation is particularly ecological relevant if it encompasses a functional separation of short- (SDD) and long-distance dispersal (LDD). It remains, however, an open question whether both parts of the dispersal kernel are similarly affected by landscape related selection pressures. We implemented an individual-based model to analyze the evolution of dispersal traits in fractal landscapes that vary in the proportion of habitat and its spatial configuration. Individuals are parthenogenetic with dispersal distance determined by two alleles on each individual‘s genome: one allele coding for the probability of global dispersal and one allele coding for the variance of a Gaussian local dispersal with mean value zero. Simulations show that mean distances of local dispersal and the probability of global dispersal, increase with increasing habitat availability, but that changes in the habitat's spatial autocorrelation impose opposing selective pressure: local dispersal distances decrease and global dispersal probabilities increase with decreasing spatial autocorrelation of the available habitat. Local adaptation of local dispersal distance emerges in landscapes with less than 70% of clumped habitat. These results demonstrate that long and short distance dispersal evolve separately according to different properties of the landscape. The landscape structure may consequently largely affect the evolution of dispersal distance strategies and the level of dispersal polymorphism.
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-47856
ER  -