Montalvo A, Conard S, Conkle M, Hodgskiss P
Am J Bot. 1997 Nov;84(11):1553.
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.
峡谷栎（Quercus chrysolepis，壳斗科）林分被保留用于薪材、火灾管理、娱乐以及作为野生动物栖息地。了解栎树繁殖生态与其遗传多样性程度之间的联系，对于制定能够维持种群长期生存能力的土地管理政策至关重要。基部萌蘖是火灾或砍伐后主要的繁殖方式，林分中经常包含成组的明显相连的树木，呈集群分布，这表明存在克隆现象。我们确定了树木集群的克隆程度，并定义了加利福尼亚南部圣贝纳迪诺山脉几乎整个东西跨度范围内六个种群的基因型空间格局和多样性。我们在五个地点的每一个都绘制了100多棵树的地图，并对每棵树在七个多态位点上进行了等位酶基因分型。我们使用这些多位点基因型鉴定克隆，每个地点平均检测到34.4±7.3（标准差）个克隆，其中大多数具有独特的基因型。一般来说，集群树木属于单个克隆，大多数克隆由少数树木组成（平均每个克隆3.4±0.6棵树）。然而，克隆大小随着个体杂合度的增加而显著增加，这表明选择可能有利于高度杂合的克隆。相对于大多数其他克隆物种的报道，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。对来自六个地点的319个克隆进行的种群遗传分析显示，各地点内遗传多样性较高（平均HS = 0.443）。总遗传多样性中只有一小部分可由地点间的变异解释（平均GST = 0.018），这与地点间的高基因流（Nm = 9.5）一致。我们在各地点内的样地中未发现显著的亚结构，各地点内的固定指数通常较小，这表明要么很少发生近亲繁殖，和/或很少有近亲繁殖的后代存活。然而，对克隆的空间自相关分析表明，在4米以下的距离存在精细尺度的遗传结构，这可能是由于种子传播有限所致。我们的数据表明，峡谷栎用于恢复的种子采集指南可以以与该研究区域内针叶树种推荐方式类似的方式来制定。
