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- Hambäck, Peter A., et al.
(författare)
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Plant trait-mediated interactions between early and late herbivores on common figwort (Scrophularia nodosa) and effects on plant seed set
- 2011
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 18:4, s. 375-381
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the interactive effects of early and late season herbivory on the growth and reproductive output of figwort (Scrophularia nodosa). The early season herbivore is a pentatomid bug that feeds on and kills the apical meristem, while the late season herbivores are 2 weevil species and a sawfly that all feed on leaves and flowers. The direct effect of early season meristem damage on plant reproduction was quite limited, although meristem damage did cause increased branching. This change in plant morphology may entail that early season herbivores have profound indirect effects on plant reproduction by affecting the abundance of and damage caused by late season herbivores. Comparisons of plants with and without early season meristem damage, natural and artificial, also suggest that plants with meristem damage are significantly shorter throughout most of the summer and receive less damage late in season. However, the reduced damage translated to increased flowering but not to increased fruit production, suggesting that the plants were able to compensate for late season damage. In the end, and despite damage, figwort was well able to tolerate the observed meristem and leaf damage.
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| 2. |
- Andersson, Petter, 1975-
(författare)
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The importance of search behavior and movements for spatial distributions of herbivorous insects
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Insect populations commonly show large spatial variation in density, and much variation have been shown to be explained by the search behavior applied by the insect when locating habitat patches. This thesis explores the importance of odor-mediated attraction for immigration rates of herbivorous insects in relation to the size of the patches and the density of host plants within the patches. By using electroantennogram and measuring moth antennal responses to sex pheromones and thereby estimating the relative odor-mediated attraction from odor patches in field experiments (Paper I, III), I show that the length of the odor plumes emanating from the patches increase proportional with the square-root of the number of odor sources. In laboratory and field experiments (with the weevils Cionus scrophulariae and C. tuberculosus and the host plant figwort Scrophularia nodosa; Paper II) and meta-analyses on multiple insect herbivores (Paper III), I examined whether the relative increase in plume length could also predict the immigration rates of olfactory searching insects in relation to patches with increasing area and increasing density of host plants. The experiments (Paper II) and meta-analyses (Paper III) showed that the observed immigration rates of olfactory searching insects was well predicted by the relative increase in plume length, as estimated from the electroantennogram measurements (Paper I, III). The importance of immigration rates, relative to the effect of emigration and local growth was also investigated for the Cionus weevils in natural S. nodosa patches (Paper IV). This study showed that the density-patch size relationships of the weevils during early season were predicted by the net scaling of emigration and immigration rates, and differences in density-patch size relationships between the two species could be explained by inter-specific differences in their emigration rates from small patches. In conclusion, this thesis shows that search behavior can be used to predict immigration rates and spatial distributions of insects, with implications for pest control, conservation ecology and general ecological theory.
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