Mortality during dispersal and the cost of host-specificity in parasites: how many aphids find hosts?
Article first published online: 25 DEC 2001
Journal of Animal Ecology
Volume 67, Issue 5, pages 763–773, September 1998
How to Cite
Ward, S. A., Leather, S. R., Pickup, J. and Harrington, R. (1998), Mortality during dispersal and the cost of host-specificity in parasites: how many aphids find hosts?. Journal of Animal Ecology, 67: 763–773. doi: 10.1046/j.1365-2656.1998.00238.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- host alternation;
- Rhopalosiphum padi;
- sympatric speciation
1. For a full assessment of explanations for the evolution of host-specificity it is necessary to estimate the probability that a dispersing parasite finds a host. We develop a method of estimating this success rate from samples of dispersing parasites and populations resident on hosts.
2. Applying this method to data on the bird cherry-oat aphid, Rhopalosiphum padi (L.), from southern Scotland in 1984–92, we estimate that 0·6% of the autumn migrants find hosts.
3. With such a low success rate, there should be selection for a broadening of host range, to include any host on which the colonist's fitness is more than about 0·6% of that on the normal hosts. We argue that neither nutrition nor the need for ‘enemy-free space’ are sufficient explanations of the host-specificity of this animal, and propose instead that it is the host's role as a rendezvous for mating that constrains the migrants to their costly host-specificity.
4. We also discuss the implications of this low success rate for the hypothesis that aphids speciate sympatrically through the formation of host races.