Mes Ted H M, Kuperus P, Kirschner J, Stepánek J, Storchová H, Oosterveld P, den Nijs J C M
Department of Parasitology and Tropical Veterinary Medicine, Institute of Infectious Diseases and Immunology, Utrecht University, Yalelaan 1, 3508 TD Utrecht, the Netherlands.
Mol Ecol. 2002 Feb;11(2):253-65. doi: 10.1046/j.1365-294x.2002.01427.x.
This study aims to identify genetically diverged clone mates in apomictic dandelions. Clone mates are defined as individuals that may have diverged as a result of mutation accumulation and that have undergone only clonal reproduction since their most recent common ancestor. Based on distinctive morphology and an aberrant and rare chloroplast haplotype, northwest European individuals of Taraxacum section Naevosa are well suited for the detection of clonal lineages in which mutation has occurred. In the case of strictly clonal reproduction, nuclear genetic variability was expected to be hierarchically organized. Nucleotide polymorphisms in internal transcribed spacer (ITS) sequences, however, were incompatible with a clonal structure of the Norwegian individuals, probably due to persistent ancestral polymorphisms that pre-date the origin of the Naevosa clone. This interpretation is supported by the presence of ITS variants in section Naevosa that were also found in distantly related dandelions. In contrast to the ITS sequence data, amplified fragment length polymorphisms (AFLPs), isozymes and microsatellites strongly supported the contention of prolonged clonal reproduction and mutation accumulation in Norwegian Naevosa. Because these markers are generally considered to be more variable and more rapidly evolving than ITS sequences, mutations in these markers probably evolved after the origin of the clone. Within the Norwegian clone, a surprising number of markers distinguished the clone mates. As a consequence, incorporation of mutation in the detection of clone mates is anticipated to have a big impact on estimates of size, geographical range and age of clones as well as on experimental designs of studies of clonal plants.
本研究旨在识别无融合生殖蒲公英中基因分化的克隆配偶体。克隆配偶体被定义为那些可能因突变积累而产生分化，且自最近共同祖先以来仅进行克隆繁殖的个体。基于独特的形态以及异常且罕见的叶绿体单倍型，蒲公英属Naevosa组的西北欧个体非常适合用于检测发生了突变的克隆谱系。在严格的克隆繁殖情况下，预计核基因变异性会呈层次结构组织。然而，内部转录间隔区（ITS）序列中的核苷酸多态性与挪威个体的克隆结构不相符，这可能是由于在Naevosa克隆起源之前就存在的祖先多态性持续存在。Naevosa组中存在的ITS变体在远缘相关的蒲公英中也有发现，这支持了这一解释。与ITS序列数据相反，扩增片段长度多态性（AFLP）、同工酶和微卫星强烈支持了挪威Naevosa长期克隆繁殖和突变积累的观点。由于这些标记通常被认为比ITS序列更具变异性且进化更快，这些标记中的突变可能在克隆起源之后才发生。在挪威克隆体内，有数量惊人的标记区分了克隆配偶体。因此，在检测克隆配偶体时纳入突变预计会对克隆的大小、地理范围和年龄估计以及克隆植物研究的实验设计产生重大影响。
