What shapes local density? The importance of migration rates and local growth for density-patch size relationships in two Cionus weevils
Version of Record online: 19 JAN 2012
© 2012 The Authors. Ecological Entomology © 2012 The Royal Entomological Society
Volume 37, Issue 1, pages 90–98, February 2012
How to Cite
ANDERSSON, P. and HAMBÄCK, P. A. (2012), What shapes local density? The importance of migration rates and local growth for density-patch size relationships in two Cionus weevils. Ecological Entomology, 37: 90–98. doi: 10.1111/j.1365-2311.2011.01339.x
- Issue online: 19 JAN 2012
- Version of Record online: 19 JAN 2012
- Accepted 24 November 2011
- Cionus scrophulariae;
- Cionus tuberculosus;
- patch size;
- scaling relationships;
- Scrophularia nodosa
1. The relative effect of migration and local growth on the spatio-temporal density-distribution of two co-existing herbivorous weevils, Cionus scrophulariae L. and C. tuberculosus Scop., in 32 host plant Scrophularia nodosa L. patches of varying sizes was investigated.
2. Predictions of the temporal development of the slope in the density-patch size relationships were derived from a basic population model with scale-dependent migration rates. The model indicated that the slopes in the density-patch size relationships during the early season should be reflected by the net scaling of immigration and emigration rates, whereas the slopes during the later season should increase as a result of local growth.
3. Emigration rates of the weevils were estimated in a field experiment, were the weevils coexisted in space and time. These results were then combined with a previous estimate of immigration rates in order to determine the net scaling of migration rates.
4. The emigration rate differed between species, caused by different movement rates in small patches, which could explain differences in the general slope of the density-patch size relationships of the weevils in the natural figwort patches throughout the summer. The slopes in the relationships in the early season were largely predicted by the net scaling of migration rates. The slope also increased in the later season for C. tuberculosus, whereas the slope decreased for C. scrophulariae.
5. It was concluded that the understanding of both inter- and intra-specific variations in density-patch size relationships of insect herbivores can be improved using population models incorporating scale-dependent migration and local growth.