Ecology Program, Department of Biological Sciences, Texas Tech University, Lubbock, Texas 79409-3131.
Am J Bot. 1998 Nov;85(11):1609-17.
We investigated clonal population structure and genetic variation in Quercus havardii (sand-shinnery oak), a deciduous rhizomatous shrub that dominates vegetation by forming uninterrupted expanses of ground cover over sandy deposits on the plains of western Texas, western Oklahoma, and eastern New Mexico. Isozyme electrophoresis (15 loci coding 11 enzymes) was used to recognize and map clones arrayed in a 2000-m transect (50-m sample intervals) and a 200 × 190 m grid (10-m sample intervals). Ninety-four clones were discovered, 38 in the transect and 56 in the grid, resulting in an estimated density of ∼15 clones per hectare. Clones varied greatly in size (∼100-7000 m), shape, and degree of fragmentation. The larger clones possessed massive interiors free of intergrowth by other clones, while the smaller clones varied in degree of intergrowth. The population maintained substantial levels of genetic variation (P = 60%, A = 2.5, H(exp) = 0.289) comparable to values obtained for other Quercus spp. and for other long-lived perennials. The population was outcrossing as evidenced by conformance of most loci to Hardy-Weinberg expected genotype proportions, although exceptions indicated a limited degree of population substructuring. These data indicate that despite apparent reproduction primarily through vegetative means, Q. havardii possesses conventional attributes of a sexual population.
我们研究了夏栎（沙生栎）的无性系种群结构和遗传变异，夏栎是一种落叶根茎灌木，在德克萨斯州西部、俄克拉荷马州西部和新墨西哥州东部的平原上，通过形成连续不断的地被植被，占据着植被的主导地位。同工酶电泳（15 个编码 11 种酶的基因座）被用于识别和绘制排列在 2000 米样带上（50 米样本间隔）和 200×190 米网格（10 米样本间隔）中的无性系。发现了 94 个无性系，其中 38 个在样带上，56 个在网格中，估计每公顷的无性系密度约为 15 个。无性系在大小（约 100-7000 米）、形状和碎片程度上差异很大。较大的无性系拥有大量的内部，没有与其他无性系的混生，而较小的无性系在混生程度上有所不同。该种群保持着大量的遗传变异水平（P = 60%，A = 2.5，H（exp）= 0.289），与其他栎属植物和其他长寿命多年生植物获得的值相当。该种群是异交的，这可以从大多数基因座符合哈迪-温伯格预期基因型比例得到证明，尽管例外情况表明种群存在一定程度的亚结构。这些数据表明，尽管夏栎显然主要通过营养繁殖进行繁殖，但它具有有性种群的常规特征。
