Current address: Bioforsk, Norwegian Institute for Agricultural Research, Høgskoleveien 7, N-1432 Ås, Norway.
Patch size effects are more important than genetic diversity for plant–herbivore interactions in Brassica crops
Article first published online: 26 FEB 2010
© 2010 The Authors. Journal compilation © 2010 The Royal Entomological Society
Volume 35, Issue 3, pages 299–306, June 2010
How to Cite
HAMBÄCK, P. A., BJÖRKMAN, M. and HOPKINS, R. J. (2010), Patch size effects are more important than genetic diversity for plant–herbivore interactions in Brassica crops. Ecological Entomology, 35: 299–306. doi: 10.1111/j.1365-2311.2010.01186.x
- Issue published online: 3 MAY 2010
- Article first published online: 26 FEB 2010
- Accepted 4 December 2009First published online 26 February 2010
- Delia radicum;
- intraspecific diversity;
- patch size;
- Plutella xylostella
1. Considerable evidence suggests that the diversity within plant communities may strongly affect the strength of species interactions, but the majority of studies only considered interspecific diversity.
2. This paper examines the effect of intraspecific genetic diversity within Brassica fields on two Brassica specialists, cabbage root fly, and diamondback moth, and on a parasitoid attacking diamondback moths. Genetic diversity was manipulated both in a replacement and an additive design.
3. Both herbivore densities and parasitism rates were higher in smaller plots, with limited responses to increased within-plot diversity. All species showed variable densities across genotypes, and preference hierarchies were species specific.
4. Responses to plot size in root flies scaled with the diameter-to-area ratio, suggesting that patch detectability affected local density, whereas responses by diamondback moths and parasitoids deviated from this ratio. These species differences could be traced to differences in the residence time within patches, where diamondback moths typically spend longer and more variable time periods in patches than root flies.
5. The lack of response to genetic diversity by both herbivores suggests that egg-laying rates are affected by decisions on the plant and not by attraction from a distance, neither to the plant itself nor the patch. Patterns of differential attack may then be due to different acceptability for studied genotypes.
6. Future theories on insect responses to spatial heterogeneity should focus on species traits and how traits interact with information landscapes in the field.