Evolution of host defense
The role of theoretical models explaining the relationships between brood parasites and their hosts
Department of Information and Computer Sciences, Nara Women's University, Nara 630-8506, Japan
S51: New models in avian host-brood parasitism systems. Convenors: Rｿskaft, E. & Soler, M.
In: Adams, N. J. & Slotow, R. H. (eds), 1999, Proceedings of 22nd International Ornithological Congress, Durban: 3146-3164.
Johannesburg: BirdLife South Africa
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Abstract: Field researches have shown that some host individuals recognize and reject parasitism but the frequency of individuals that reject parasitism ranges from 0 % to 100 % depending on host population. Host populations that do not show perfect defense despite being parasitized have been a point of controversy. Do these hosts behave adaptively or do they only lack adaptive characteristics in evolutionary time scale? I constructed mathematical models to describe the relationships between brood parasites and their hosts and analyzed how the host defense spreads under selection pressure imposed by the parasite. The main results are 1) host may not establish perfect defense. 2) distribution of host defense levels is crucially affected by the parasite breeding strategy as specialized or generalized. Population dynamics is essential to these results. By measuring and estimating biological quantities (breeding parameters etc.), we would be able to resolve a long standing question - which hypotheses, evolutionary lag or equilibrium, better explain the well studied cases of the Common Cuckoo, Cuculus canorus, and the Brown-headed Cowbird, Molothrus ater. I suggest the usefulness of theoretical study to explore problems of brood parasitism with close cooperation with empirical study.
Symposium Talk at 22nd International Ornithological Congress in Durban, South Africa, 1998:
The role of theoretical models explaining the relationships between brood parasites and their hosts (163kB in PDF format)