Genetic adaptation of tree populations to natural selection

云杉自然种群分布于北海道中部从海拔300米的低地到海拔1400米的高寒地带。我们研究了这些自然种群的形态和生理特征，分布在海拔300 ~ 1400m之间。形态性状（针叶密度和针叶厚度）和生理性状（叶绿素a+b /氮比值）均呈海拔梯度。由于在海拔530、730、930和1100m的移植重复株中也观察到相似的生长曲线，表型可塑性可能是造成这种海拔差异的原因之一。通过相互移植实验，我们发现萨沙林冷杉对同一山坡的原始海拔带表现出较强的局部适应性。因此，我们认为格列氏矮种对海拔的遗传适应程度低于沙沙林矮种。随后，我们利用微卫星和等位酶标记来评估格列氏矮豆居群间的遗传分化，并检测非中性基因座对海拔自然选择的影响。微卫星标记获得的遗传分化程度低于等位酶标记。微卫星基因座与环境无关。相比之下，等位酶仅在高山群体中存在一定的变异。以往的研究表明，高寒地区矮居群的幼苗生长明显低于中等海拔地区的矮居群。这些结果表明，高寒地区的矮居群与北海道中部地区的矮居群可能具有不同的生态型。

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.