Levy F, Antonovics J, Boynton J E, Gillham N W
Department of Biological Sciences, East Tennessee State University, Johnson City 37614, USA.
Heredity (Edinb). 1996 Feb;76 ( Pt 2):143-55. doi: 10.1038/hdy.1996.22.
Hierarchical sampling from populations, incipient and recognized varieties within Phacelia dubia and P. maculata has revealed high levels of intraspecific polymorphism in chloroplast DNA. Much of the variation is partitioned between populations as evidenced by population-specific variants at fixation in all three populations of P. dubia var. interior and in both populations of P. maculata. Nine of 16 populations were polymorphic for cpDNA haplotypes. A total of 16 haplotypes was found in a sample of 106 individuals; the most common occurred in eight of the 16 populations and in 31 per cent of the individuals in the entire sample. A phylogenetic analysis revealed four basic plastome types. The two major groups of plastomes were separated by four independent base-pair mutations which suggests an ancient split in the evolution of plastid genomes. Representatives from each major plastome division were found in each of five populations spanning two allopatric varieties of P. dubia. The geographical distribution of haplotypes and lack of evidence for recent admixture argue against migration as a source of the polymorphism. It is more likely that the current taxonomic varieties are descendants of a polymorphic common ancestor.
对可疑紫草（Phacelia dubia）和斑点紫草（P. maculata）的种群、初始变种和公认变种进行分层抽样，结果显示叶绿体DNA存在高水平的种内多态性。许多变异在种群之间进行了划分，这在可疑紫草变种内的所有三个种群以及斑点紫草的两个种群中固定的种群特异性变体中得到了证明。16个种群中有9个种群的叶绿体DNA单倍型具有多态性。在106个个体的样本中总共发现了16种单倍型；最常见的单倍型出现在16个种群中的8个种群中，占整个样本中个体的31%。系统发育分析揭示了四种基本的质体基因组类型。两组主要的质体基因组被四个独立的碱基对突变分开，这表明质体基因组进化中存在古老的分歧。在跨越可疑紫草两个异域变种的五个种群中的每一个种群中都发现了每个主要质体基因组分支的代表。单倍型的地理分布以及缺乏近期混合的证据表明迁移不是多态性的来源。目前的分类变种更有可能是多态性共同祖先的后代。
