球状绿藻的隐性生物多样性及其分类学进展

Cryptic biodiversity of coccoid green algae and progress in the phylogenic studies

球状绿藻主要指绿藻门中多为单细胞,形状为球形、近球形,或由球形衍生出来的其他形状的藻类。球状绿藻分布广泛,遍布全球,生活于淡水、海水和亚气生等生境中,其相似的简单形态下隐藏着复杂的物种多样性。球状绿藻分类学上主要位于绿藻门的两纲四目及其一些独立支系的类群。球状绿藻分类学正由传统的基于形态特征向基于分子信息的复合分类方法转变。球状绿藻隐性的物种多样性涉及约40属,其中15属是依据新标本材料而建立的新属,12个属是依据新证据建立的新组合。本文重点介绍了1998年以后在共球藻纲和绿藻纲中新发现和命名的单细胞球状绿藻,介绍了它们的形态特征、分类学迁移及理由,特别对常见的小球藻属和栅藻属的分类学概念变迁作了详细介绍,对一些尚没有中文名的拉丁学名给出了中文命名。另外,本文讨论了基于DNA的分类学方法在球状绿藻分类学中的应用,目前系统发育位置的不同已经成为球状绿藻分类的主要依据。目前球状绿藻分类面临的问题是大多分类位置未用分子系统发育方法的验证。未来,球状绿藻分类学家应用系统发育研究结合形态学研究探索单细胞球状绿藻的生物多样性。

Coccoid green algae primarily refers to algae that are solitary living organisms spherical or ellipsoid in shape. It is widely distributed around the world living in freshwater, seawater and subaerial habitats. The similarity in shape of these organisms hides a huge cryptic biodiversity. Coccoid green algae phylogeny belongs primarily to four orders and some incertae sedis taxa of two classes. This paper reports the changes in taxonomic study methods of coccoid green algae and the resulting cryptic biodiversity that has been discovered. A total of 15 new genera （now totaling 40 genera for coccoid green algae） and 12 new combinations were discovered from collected specimens. This paper focuses on the discovery and renaming of coccoid green algae in Trebouxiophyceae and Chlorophyceae after 1998. We present the diagnostic features, phylo- genic changes and reasons for the discoveries and remaining. The changes in the genera of Chlorella and Scenedesmus are presented in details. We also discuss the application of DNA-based methods in taxonomic identification of coccoid green algae and how differences in phylogenetic position have become the main basis for taxonomic identifaction. Finally, we address the problems in phylogenic studies ofcoccoid green algae by which taxonomic location based on the morphological features have not yet been validated by phyloge-netic methods. In the future, algae taxonomists should combine phylogenetic methods with morphological methods to explore the cryptic biodiversity of coccoid green algae.