Population biological study on extinction and persistence of natural populations.

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This cooperative research project was intended to study key processes for natural populations of animals and plants lead to extinction, in which population ecologists, community ecologists, epidemiologists, population geneticists and other researchers in related fields collaborate closely and identify key issues of basic biology needed for effective conservation of endangered species. We first had a meeting in which we discussed the potential problems in different aspects of this science. Then each member studies his/her made own progress in collaboration with others.(1) Virus disease that has spread among several carnivores in Tama district, Tokyo, Japan, has been studied using both epidemiological study and gene sequence analysis of virus. Coevolution of Gemini virus and its host plant has been examined by genomic analysis.(2) The pollinator-based mechanisms by which high genetic diversity is maintain are studied in tropical rain forest in Malaysia. In Bonin islands, invader honey bee and resident species are compared with respect to foraging and pollination behavior, and their differential effect on plant fecundity and survivorship. Effect of novel invader to resident species in fluctuating and heterogeneous habitat is examined.(3) Fluctuating asymmetry of freshwater fish (Medaka) is measured as candidate traits revealing basic fitness. Genetic diversity is studied for perennial plant populations of river bed that are frequently disturbed. Theoretical study of inbreeding depression has been carried out.(4) The effect of spatial structure of an endangered plant and mutualistic/herbivorous insects is studied from the viewpoint of meta-population dynamics.(5) Methods for estimating past mass extinction events from ancestral phylogeny of extant species and those for estimating past population sizes from genetic diversity are developed.