Department of Sustainable Resource Sciences, Graduate School of Bioresources, Mie University, Tsu, 514-8507, Japan.
Department of Applied Biology and Food Sciences, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, 036-8561, Japan.
Heredity (Edinb). 2020 Oct;125(4):240-252. doi: 10.1038/s41437-020-0334-8. Epub 2020 Jun 30.
The spatial patterns of non-neutral genetic variations at fine spatial scales and their possible associations with microenvironments have not been well-documented for tree populations. Based on 25-32 SNP markers, we examine whether non-neutral SNPs and their associations with microenvironments can be detected in FcMYB1603, a gene homologous to that encoding a protein induced by drought stress in Arabidopsis thaliana for the 166 adult trees in a 1-ha plot in a mature population of Fagus crenata. In the 83 individuals of a younger cohort of below canopy trees, the nonsynonymous SNP at locus FcMYB1603_684 exhibited a spatial signature representing a departure from the expected spatial patterns of neutral genetic variation. Evaluations of non-neutrality for this locus were robust against the potential risks of false positives due to the low number of SNP loci, a low criterion set for minor allele frequency, and any edge effect on the trees' spatial structure. An older cohort exhibited no signal of the existence of non-neutral genetic variation, suggesting that temporal fluctuation in the microenvironmental conditions on the forest floor may have exposed different cohorts to different magnitudes of selection pressure. Although genotypes of the locus showed a spatial association with a microenvironmental variable potentially related to soil moisture, the present study was subject to a limitation due to the generally low polymorphism of nonsynonymous loci within the single plot, which suggests that it will be important to replicate the study design in order to carry out research on fine-scale non-neutral genetic variations.
在精细的空间尺度上，非中性遗传变异的空间模式及其与微环境的可能联系在树木种群中尚未得到很好的记录。基于 25-32 个 SNP 标记，我们研究了在 Fagus crenata 成熟种群的 1 公顷样地中，166 棵成年树的一个基因 FcMYB1603（与拟南芥干旱胁迫诱导蛋白编码基因同源）中，非中性 SNP 及其与微环境的关联是否可以被检测到。在一个较年轻的林下层树木队列的 83 个个体中，位于 FcMYB1603_684 基因座的非同义 SNP 表现出一种空间特征，表明其偏离了中性遗传变异的预期空间模式。该基因座的非中性评估对由于 SNP 基因座数量少、次要等位基因频率的标准设置低以及树木空间结构的边缘效应而导致的假阳性风险具有稳健性。一个较老的队列没有显示出非中性遗传变异存在的信号，这表明林下地被物微环境条件的时间波动可能使不同的队列面临不同程度的选择压力。尽管该基因座的基因型与一个潜在与土壤水分相关的微环境变量表现出空间关联，但本研究受到单个样地中非同义基因座普遍低多态性的限制，这表明为了开展对精细尺度非中性遗传变异的研究，重复该研究设计将非常重要。
