短孢角毛藻相似种类的形态学和系统学研究

Morphological and Phylogenetic Studies on Chaetoceros brevis Schütt and Its Allied Taxa

短孢角毛藻的形态特征多变,容易导致物种的错误鉴定,并且其与若干相似种类之间存在物种混淆的情况。基于建立的单克隆培养藻株,结合生活史中形态特征的连续观察,以及基于目标基因序列分析的分子系统学数据,对短孢角毛藻(Chaetoceros brevis Schütt)及其相似种类的形态学和系统学进行了研究。丰富了短孢角毛藻休眠孢子的形态学描述,报道了一个新的特征:休眠孢子壳面上刺的末端具有帽状结构,该特征未报道于其他角毛藻种类,可作为短孢角毛藻的标志性特征。报道了我国角毛藻属的1个新记录种——拟短孢角毛藻(C.pseudobrevis Pavillard),该种具有独特的形态学特征,以及独立的系统学位置,应是一个独立的物种,而非短孢角毛藻的同种异名。垂缘组角毛藻的种类在系统发育树中显示出较好的单系起源,链端角毛及其走势是否可以作为该类群的共享特征,目前尚难做出定论。

Because of the variation of some key morphological characteristics and the subjective influences from researchers,the mis-identification has occurred commonly to Chaetoceros brevis.Meanwhile,there are still some debate on the species sharing very similar morphology with C.brevis,for example whether they could be ranked as a separated species or just a variety as C.brevis var.pseudobrevis.To solve the above questions,several monoclonal stains were established,their morphology and systematic were studied based on the combination of continuously morphological observation in the life cycle and molecular data from some target genes.One new morphological characteristic was found in C.brevis,i.e.,the cap-like structure on the top of spins on the surface of resting spore,which has never been reported in other Chaetoceros species,and could be a unique feature to identify C.brevis.A newly recorded diatom species for China was observed,C.pseudobrevis.Combine the morphology and molecular data,it was shown that C.pseudobrevis should be a separate taxa,not a variety of C.brevis.In the phylogenetic trees,the taxa in section Laciniosa clustered in the same clade,which shown the monophygeny and matching with the morphological grouping.But so far it is difficult to confirm the commonsharing features for this section.