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- Title
Evolution of contest competition and its effect on host-parasitoid dynamics
- Authors
Tuda, Midori; Iwasa, Yoh
- Abstract
In experimental populations of the cowpea bean weevil Callosobruchusmaculatus (Coleoptera: Bruchidae) and a parasitic wasp Heterospilus prosopidis (Hymenoptera: Braconidae), large changes in the abundancesand the fluctuations of both species occurred after approximately 20generations. In this paper, we examine the hypothesis that this observed change in the dynamics may have been caused by an evolutionary shift in the mode of competition among the bean weevils. A Nicholson-Bailey type model is developed using parameters measured from the experiments. The host larvae can differ in the type of competitive behavior that they exhibit, which can be either of a contest type or of a scramble type. If a bean contains one or more larvae of the contest type, only one of these will survive and any scramble-type larvae in the bean will be killed. If no contest-type larvae are present within abean, multiple individuals of the scramble type can emerge from a single bean. The model assumes many genotypes, differing in the fraction of offspring of the two types. If a high per capita resource availability is maintained, then the scramble type is selected for, but if resources are limited, then the contest type is selected for. The host population at the start of the experiment, taken from a stock culture, was composed mostly of the scramble type. The model is successfulin explaining the initial quick increase in the host's abundance, followed by the evolutionary increase in the fraction of the contest type among hosts, resulting in the more stable population dynamics of the host-parasitoid system, as observed in the experiments. However, it predicts a parasitoid abundance much higher than that observed. We discuss alternative hypotheses to explain the observed evolutionary shift in the population dynamics. We also examine the effect of the difference in size of the beans in the stock culture and those used in the experiments.
- Subjects
EVOLUTIONARY theories; ECOLOGY
- Publication
Evolutionary Ecology, 1998, Vol 12, Issue 7, p855
- ISSN
0269-7653
- Publication type
Article
- DOI
10.1023/A:1006550817371