通过ITS序列对21种中国外来苋属植物进行系统进化关系研究.通过ITS序列种间、种内遗传距离分析,发现苋属种间变异为0~0.0551,种内变异为0~0.0092.使用TAXON DNA软件分析ITS序列种间、种内变异的分布图看出规律,结果表明苋属ITS序列的种间变异适中,种间变异明显大于种内变异.采用最大似然法(ML)构建的系统树将中国苋属分为5或6个进化支(根据自展支持率取值不同).异株苋亚属长芒苋和苋亚属刺苋聚类在一起,西部苋和糙果苋单独成为一个进化支.苋亚属中苋组苋亚组反枝苋和绿穗苋亚组鲍氏苋有着更近的亲缘关系,苋组苋亚组尾穗苋和绿穗苋亚组绿穗苋、繁穗苋等亲缘关系更近.白苋亚属分为2或3个类群,根据自展支持率取值不同,合被苋可以和白苋、北美苋并为一支,也可以单独成为一支.综上所述,该文认为苋属经典分类体系中3亚属或2~3组的分类地位不成立,建议中国苋属采取5组2亚组或6组2亚组的分类体系.5组2亚组分别由长芒苋组、糙果苋组、苋组(苋亚组和绿穗苋亚组)、白苋组和凹头苋组组成.其中,合被苋也可从白苋组分出,单独构成1组,形成6组2亚组的分类体系.表明该序列对苋属大部分种类分类效果较好,对西部苋和糙果苋复合群,绿穗苋复合群以及白苋亚属的分类价值不高.%We collected 21 species of Amaranthus and carried out phylogenetic evolutionary studies on ITS sequences of the 21 species of Amaranthus. Through interspecific and intraspecific genetic distance analysis of ITS sequences, the values of interspecific variation were 0-0.0551 and intraspecific variation were 0-0.0092. Using TAXON DNA software to build bar-coding gap figure of ITS sequences, we could see interspecific variations of Amaranthus species were moderation. And inter-and intraspecific variation were overlapping in a few. In addition, five or six clades could be separated on the phylogenetic tree constructed by ML methods (according to the bootstrap value). Such as, A. plameri (subgen. Acnida) and A. spinosus ( subgen. Amaranthus ) clustered together. A. tuberculatus and A. rudis formed a sole clade jointly. A. retroflexus (subgen. Amaranthus, sect. Amaranthus, subsect. Amaranthus) and A. powellii (subgen. Amaranthus, sect. Amaranthus, subsect. Hybrida) had more close relationship. A. caudatus (subgen. Amaranthus, sect. Amaranthus, subsect. Amaranthus) and A. hybridus complex (including A. hybridus, A. cruentus and A. hypochondriacus) (subgen. Amaranthus, sect. Amaran- thus, subsect. Hybrida) were closer more. Subgen. Albersia was divided into two or three groups, A. polygonoides could be merged into A. albus and A. blitoides, or form a sole clade (Clade 6) by itself according to the bootstrap value. Therefore, categories of three subgenus or two to three sections based on traditional classification systems were problematic, we sugges-ted that classification of Amaranthus in China should be divided into five sections and two subsections, or six sections and two subsections. The five sections and two subsections respectively were sect. Saueranthus including A. palmeri and A. spino-sus, sect. Acnida (A. tuberculatus and A. rudis), sect. Amaranthus including subsect. Amaranthus (A. retroflexus and A. powellii) and subsect. Hybrida (A. hybridus, A. hypochondriacus, A. cruentus and A. caudatus), sect. Albersia including A. blitum, A. viridis, A. deflexus, A. tricolor, A. graecizans, A. crispus, A. tenuifolius and A. standleyanus, and sect. Blitopsis including A. albus, A. blitoides, A. capensis and A. polygonoides. Most Amaranthus Pecies could be discriminated, only a few allied species (A. rudis and A. tuberculatus complex, and A. hybridus complex) and species under subgen. Albersia could not be separated clearly.
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