A Re-Examination of the Algal Class Xanthophyceae Based Upon 18S r RNA and rbc L Sequence Analysis

安徒生DEB-9806743，黄藻纲，包括一个由大约600种黄绿色藻类组成的多样化组合。一些物种存在于土壤中，但大多数存在于水生环境中，在那里它们和其他藻类一起构成食物链的基础。除了极少数例外，还没有人用现代生物技术研究过叶黄植物。事实上，许多物种自从近50年前最初基于光学显微镜观察而被描述以来，就没有被重新检查过。在历史上，物种的分类是基于它们的“生命形式”，即：1)变形体细胞，2)无鞭毛的有壁细胞，3)有鞭毛的细胞，4)丝状细胞，5)胶状囊膜中的有壁细胞，或6)没有横壁的多核细丝。较小的鞭毛物种通常被认为比较大的、丝状和管状的物种更原始。在初步的系统发育分析中，我们已经发现，一些丝状生物与球状生物的相似性大于它们彼此之间的相似性。同样，也没有发现几种管水母类生物有密切的亲缘关系。初步数据还显示，目前被归入黄藻纲的一个物种应该被归入一个完全不同的藻类群。安德森和贝利是唯一有资格进行这项研究的人，他们将完成对叶黄科传统分类的期待已久的重新评估。目标是1)确定一组可以明确归入黄藻类的物种，2)为这一组建立一个现代分类，以及3)在其他地方重新归类属于其他藻类组的那些物种。

Andersen DEB-9806743 The class Xanthophyceae includes a diverse assemblage of approximately 600 species of yellow-green colored algae. Some species are found in soil, but the majority are found in aquatic environments where they, and other algae, form the base of the food chain. With few exceptions, xanthophytes have not been studied using modern biological techniques. In fact many species have not been re-examined since they were described originally on the basis of light microscopic observations nearly 50 years ago. Historically, species have been classified based upon their "life form," i.e., 1) amoeboid cells, 2) walled cells lacking flagella, 3) flagellate cells, 4) filamentous cells, 5) walled cells held in a gelatinous envelope, or 6) multinucleate filaments that lack cross walls. The smaller flagellate species are generally regarded as being more primitive than the larger, filamentous and siphoneous forms. In preliminary phylogenetic analyses, we already have found that that some filamentous organisms are more similar to coccoid organisms than they are to each other. Similarly, several siphoneous organisms were not found to be closely related. Preliminary data also showed that a species currently placed in the Xanthophyceae should be classified within a completely different algal group. Anderson and Bailey, uniquely qualified for this study, will accomplish a long-overdue re-evaluation of the traditional classification of Xanthophyceae. The objectives are 1) to identify a group of species that can unequivocally be placed in the Xanthophyceae, 2) to construct a modern classification for the group, and 3) to re-classify elsewhere those species that belong in other algal groups.