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 (367KB)
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21,958,000 Yen (FY1998; 6,992,000 Yen)
Environmental threats, such as habitat size reduction or environmental pollution, may not cause immediate extinction of a population but shorten the expected time to extinction. We develop a method to estimate the mean time to extinction for a densitydependent population with environmental fluctuation, and discuss the relative magnitude of impact caused by the reduction in the habitat area and the reduction of survivorship due to environmental pollution. Second, we studied two population systems; Aster kantoensis natural populations and Callosobruchus chinensis experimental systems. Based on field survey of A. kantoensis, a lattice model was constructed to calculate an extinction rate of the metapopulation. In experimental systems, a black mutant strain was used for estimating projection matrix. Based on the projection matrix of each genotype, extinction rate of a metapopulation is calculated using an individual-based model. Third, the simulation study indicated that the number of accumulated deleterious mutation significantly change due to changing the shape of the habitat. The extinction risk increased when the habitats were long and narrow and when the habitats were subdiveded. The present simulation models will be useful to determine conserved area of endangered species.
Extinction risk, Metapopulation, Mutation meltdown, population viability analysis, computer simulation