Conservation for regional populations of endangered plant species growing in seminatural ecosystems

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We investigated habitat condition, reproductive characteristics and population structure in three local populations of Erythronium japonicum in Hokkaido. This understory herb is one of the most typical spring ephemerals in Japan, and the habitat of the species has been threatened by land use changes. The study sites are Tanno town near the easternmost part of the distribution range of the species, Tossho-zan in Asahikawa City, and Pin-neshiri in Shintotsukawa town.The temperature condition of growing season was harsher in Tanno town than in Tosshozan and Pin-neshiri.Although E. japonicum seems to be an outcross species in the Honshu island, pollination experiments showed that the Tanno population has not only self compativility but also automatic self pollination ability. The Asahikawa population slightly has both abilities, but the Pin-neshiri population does not. Maximum individual size identified by leaf area was decreasing order from the Pin-neshiri, the Tosshozan, to the Tanno populations. The extent of both abilities seems to be accompanied with the habitat conditions of the study sites.Population dynamics was simulated by Leslie matrix model for the Tossho-zan and the Tanno populations. Regardless to initial growth rates of population, the probabilities of extinction were low not only in the Tossho-zan population but also in the Tanno population.Based on the results mentioned above, it is concluded that the three populations studied are in stable conditions, and have low probabilities of extinction. Further studies will be needed for genetic diversities of the populations, and for the presence of inbreeding depletion as a consequence of self compatibility.