Genetic adaptation of tree populations to natural selection

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Natural populations of Picea glehnii distributes in various altitudes from lowland nemoral (300m asl.) to alpine zone (1400m asl.) in central Hokkaido. We investigated morphological and physiological traits of needles from these natural populations ranging from 300m to 1400m asl.Clines along the altitude were detected in both morphological (needle density and thickness) and physiological traits (the ratio of chlorophyll a+b / nitrogen). Since the similar clines were observed in altitudinal transplant replications (530, 730, 930, and 1100m asl.), phenotypic plasticity might be one of the causes of this altitudinal differences. We found that Abies sachalinensis showed strong local adaptation to the original altitudinal zones in the same mountainous slope through the reciprocal transplant experiments. Therefore, we concluded that the extent of genetic adaptation to altitude of P. glehnii was lower than that of A. sachalinensis. Subsequently, we used microsatellite and allozyme markers, in order to evaluate genetic differentiation among populations of P. glehnii and to detect non-neutral loci against natural selection along the altitude. The extent of genetic differentiation obtained by microsatellite markers was lower than that by allozyme markers. None of microsatellite loci were related to the environment. In contrast, certain allozyme variation was detected only in alpine population. Previous studies had revealed that seedling growth from dwarf populations in alpine zones was significantly lower than that from middle-altitude populations. These findings indicated that dwarf populations in alpine zones might be different ecotype from other populations of P. glehnii in central Hokkaido.