| Project/Area Number |
13640621
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生態
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| Research Institution | Hokkaido University |
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Principal Investigator |
NISHIMURA Kinya Hokkaido University, Graduate School of Fisheries Sciences, 助教授 (30222186)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2001: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Cannibalism / Evolutionary branching / Game / Phenotype / Natural Selection / ゲーム形 / 進化ダイナミクス / 突然変異 / 形質適応進化 / 形質分岐 / 収束安定 / 進化 / 形態 / コスト |
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| Research Abstract |
Evolutionary branching, that is coevolutionary phenomenon of development of two or more distinctive traits from a single trait in a population, is the issue of recent study of adaptive dynamics. In the previous studies, trait variance is a minimum requirement for evolutionary branching, and it did not play important role for the evolutionary pattern of branching. Here I demonstrate that trait evolution exhibits variety of evolutionary branching paths starting from an identical initial trait to different evolutional terminus traits only changing assumption of trait variance. The key property for this phenomenon is the topological configuration of equilibria and initial point in the manifold of protected dimorphism in which the dimorphism branches developing. This suggests that the existing monomorphic or polymorphic set in a population not a unique inevitable consequence from an identical initial phenotype.
I analyzed the attainable state of an evolutionary cannibalism game within a framework that reflects the minimum essence of cause-effect in the cannibalism phenomenon. No morphological specialization and no size priority of cannibalism individuals are assumed as conservative situations in which I analyze the possibility of cannibalism. Cannibalism would be possible under the conservative condition, if initially the wild population's cannibalism rate is not sufficiently lower than a threshold value. Crowding and/or low availability of alternative prey with the fear of starvation facilitates cannibalism evolution. Energy gain from conspecific prey would be attenuated by costs of counterattacks by conspecific victims and by challenge cost of its own. Discounting net intake energy required in the arms race for cannibalism challenge result in a relative disadvantage of having a high cannibalism rate and makes an evolutionary equilibrium of low cannibalism rate, even when potential profitability of conspecific prey is high.
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