Spatio-temporal dynamics of alpine herbs along snowmelt gradient and prediction of change in global environment

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Genetic structure of natural plant populations is determined by spatio-temporal heterogeneity and interactions of various biotic as well as abiotic environmental factors. In alpine environments, with heavy snowfall, the occurrence of plants within snow-patches (snowbed plants) can have a strong impact on gene flow via pollen flow among patches. To examine the relationship between landscape features and spatial pattern of genetic variation in alpine environments, we conducted field observations such as differentiation of flowering phenology, behavior of pollinators and also examined population genetic structures using allozyme electrophoresis. This study project was conducted at three mountain ranges, i.e., the central part of the Taisetsu Mountains in Hokkaido, Japan, Tateyama Mountains in Toyama, Japan and Rocky Mountains, Colorado, USA.We examined various plant taxa (Peucedanum multivittatum, Veronica stelleri, Gentiana nipponica, Phyllodoce caerulea, P.aleuticca, Dryas octopetala, Japonolirion ozense, Sieversia pentapetala, Erythronium grandiflorum) in this study project. In general, we found that phonologically asynchronous populations are packed within a local area in alpine snowbeds because flowering season of alpine plants highly depends on the timing of snowmelt. The interaction through pollination between the sympatric species is strong enough to cause a phenotypic change in mating system even within a local area. Restriction of gene flow due to phonological separation and possible differential selection along snowmelt gradient may produce genetic clines at microgeographic scale. Furthermore, to forecast the future population structure under stochastically varying environment, plant population dynamics were investigated by application of the transition matrix model. As a result, eigenvalue sensitivity analysis of a population projection matrix that is revealed near equilibrium can give useful information about the sensitivity of the equilibrium population.