Population structure, genetic diversity, and clone formation in Quercus chrysolepis (Fagaceae).
Population structure, genetic diversity, and clone formation in Quercus chrysolepis (Fagaceae).
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DOI：
10.2307/2446617
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发表时间：
1997-11
影响因子：
3
通讯作者：
A. Montalvo;S. Conard;M. Conkle;P. Hodgskiss
中科院分区：
文献类型：
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作者：
A. Montalvo;S. Conard;M. Conkle;P. Hodgskiss
峡谷中的活橡树（Quercus chrysolepis，壳斗科）被保留用于薪材、消防、娱乐和野生动物的栖息地。有关橡树繁殖生态与其遗传多样性程度之间联系的信息对于制定维持种群长期生存能力的土地管理政策非常重要。基部发芽是火灾或砍伐后繁殖的主要方式，林分中经常包括成群分布的明显相连的树木，这表明克隆。我们确定了树丛克隆的程度，并定义了南加州圣贝纳迪诺山脉几乎整个东西走向的六个种群的空间格局和基因型多样性。我们在 5 个位点的每个位点绘制了 100 多棵树，并对每棵树的 7 个多态位点的同种酶进行了基因分型。我们使用这些多位点基因型鉴定了克隆，每个位点平均检测到 34.4 ± 7.3 (SD) 个克隆，其中大多数具有独特的基因型。一般来说，簇状树属于单个克隆，大多数克隆由少数树组成（平均值 = 每个克隆 3.4 ± 0.6 棵树）。然而，随着个体杂合性的增加，克隆大小显着增加，这表明选择可能有利于高度杂合的克隆。与大多数其他克隆物种的报告相比，克隆多样性和均匀度较高；平均 97% 的克隆具有不同的基因型，辛普森多样性指数平均为 0.95 ± 0.02。对来自 6 个位点的 319 个克隆进行的群体遗传分析揭示了位点内的高遗传多样性（平均 HS = 0.443）。总遗传多样性中只有一小部分可以通过位点之间的变异来解释（平均 GST = 0.018），这与位点之间的高基因流一致（Nm = 9.5）。我们发现地点内的地块之间没有显着的子结构，并且地点内的固定指数通常很小，这表明几乎没有发生近交，和/或很少有近交后代存活。然而，克隆的空间自相关分析表明，在 4 m 以下的距离内存在精细遗传结构，这可能是由于种子传播有限。我们的数据表明，用于恢复的峡谷活橡树种子收集指南可以按照类似于研究区域内针叶树物种建议的方式指定。
Stands of canyon live oak (Quercus chrysolepis, Fagaceae) are maintained for fuelwood, fire management, recreation, and as habitat for wildlife. Information about the link between the oak's reproductive ecology and its extent of genetic diversity is important in developing land management policies that will maintain the long-term viability of populations. Basal sprouting is the primary means of reproduction following fire or cutting, and stands frequently include groups of visibly connected trees in a clustered distribution that suggests cloning. We determined the extent to which clusters of trees were clonal and defined the spatial pattern and diversity of genotypes for six populations across nearly the entire east-west extent of the San Bernardino Mountains in southern California. We mapped over 100 trees at each of five sites and genotyped each tree for allozymes at seven polymorphic loci. We identified clones using these multilocus genotypes and detected an average of 34.4 ± 7.3 (SD) clones per site, most of which had unique genotypes. In general, clustered trees belong to single clones and most clones consist of few trees (mean = 3.4 ± 0.6 trees per clone). However, clone size increased significantly with increased individual heterozygosity, suggesting that selection may favor highly heterozygous clones. Clonal diversity and evenness were high relative to reports for most other clonal species; an average of 97% of clones had distinct genotypes, and Simpson's index of diversity averaged 0.95 ± 0.02. Population genetic analyses of 319 clones from six sites revealed high genetic diversity within sites (mean HS = 0.443). Only a small proportion of the total genetic diversity was explained by variation among sites (mean GST = 0.018), which is consistent with high gene flow among sites (Nm = 9.5). We found no significant substructure among plots within sites, and fixation indices within sites were generally small, suggesting that either little inbreeding occurs, and/or few inbred progeny survive. However, spatial autocorrelation analysis of clones indicated fine-scale genetic structure at distances under 4 m, possibly due to limited seed dispersal. Our data suggest that guidelines for seed collection of canyon live oak for use in restoration can be specified in a manner similar to that recommended for conifer species within the region studied.