Resource Exploitation Strategies under Different Resource Quality and Competition in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)
Date Issued
2007
Date
2007
Author(s)
Wu, Wen-Hsin
DOI
zh-TW
Abstract
The marginal value theorem (MVT) predicts that a single forager should exploit resource until their instantaneous rate of fitness gain drops below the mean of expected rate in the whole environment. In other words, the higher the quality of resource patch, the longer an individual should remain on it. We tested this prediction in the seed beetle Callosobruchus maculatus, whose female can adjust its oviposition behaviors based on host qualities, such as size, number and egg density. We manipulated different host quality patch to investigate the behavior strategies of the seed beetles. Our results showed that the performance of female seed beetles matched the MVT’s prediction under treatments of host size and number. Surprisingly, when treated them with already-parasitized hosts, females performed binomonal behaviors. Some members of population tended to leave early, whereas the others tended to remain on the resource for longer time, further exploit the resource. The MVT assumes the condition without competitors, but animal do not always forage alone. Some theoretical model predicts that forager should stay in the patch longer than when competitors are present. Hence, we investigated the effect of direct competition on resource exploitation strategies. The effect of direct competition was similar to the treatment of already-parasitized hosts. It revealed that the egg density is not only serving as a host qualities indicator, but also represents the existence of competition, which causes the polymorphism of resource exploitation in the seed beetle. The adaptive value of different strategies will be discussed.
Subjects
四紋豆象
邊際價值理論
資源區品質
競爭
離開資源區
Callosobruchus maculatus
optimal foraging
patch quality
Type
thesis
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