Jo Bok Yeon, Shin Woongghi, Boo Sung Min, Kim Han Soon, Siver Peter A
Department of Biology, Chungnam National University, Daejeon 305-764, KoreaDepartment of Biology, Kyungpook National University, Daegu 702-701, KoreaDepartment of Botany, Connecticut College, New London, Connecticut 06320, USA.
J Phycol. 2011 Apr;47(2):415-25. doi: 10.1111/j.1529-8817.2010.00953.x. Epub 2011 Mar 1.
The genus Mallomonas, a common and often abundant member of the planktic community in many freshwater habitats worldwide, consists of 180 species divided into 19 sections and 23 series. Classification of species is based largely on ultrastructural characteristics of the siliceous scales and bristles that collectively form a highly organized covering over the cell. However, the relative importance of the different siliceous features of the scales, such as the dome, V rib, and secondary structures, as well as the different types of scales, in understanding the evolution and phylogeny of the genus is little known. In this study, we investigated the scale and bristle ultrastructure, along with sequences of three genes, for 19 isolates (18 species) of Mallomonas (18 isolates were from Korean habitats). The isolates represented nine of the 19 sections. Sequences for both the nuclear SSU and LSU rDNA and plastid LSU of RUBISCO (rbcL) genes for each of the 19 Mallomonas isolates and four outgroups were determined. Bayesian and maximum-likelihood (ML) analyses of the data revealed that Mallomonas consists of two strongly supported clades. Mallomonas bangladeshica (E. Takah. et T. Hayak.) Siver et A. P. Wolfe was at the base of the first clade that included taxa from the sections Planae and Heterospinae, both of which lack a V rib on the shield of the scales. Our results indicated that the sections Planae and Heterospinae should be combined. The second clade, with Mallomonas insignis Penard and Mallomonas punctifera Korshikov at the base, contained taxa from the sections Mallomonas, Striatae, Akrokomae, Annulatae, Torquatae, Punctiferae, and Insignes, all of which have V ribs or well-developed marginal ribs on the scales. Sister relationships between Mallomonas and Striatae were strongly supported, but interrelations among the remaining sections were not resolved, probably due to inclusion of too few species. Our results suggest that the current classification of the genus Mallomonas at the section level will require some revision. Additional species will need to be added in future analyses.
马洛莫纳斯属是全球许多淡水生境中浮游生物群落常见且数量往往丰富的成员，由180个物种组成，分为19个组和23个系。物种分类主要基于硅质鳞片和刚毛的超微结构特征，这些鳞片和刚毛共同在细胞上形成高度有组织的覆盖物。然而，鳞片不同硅质特征（如穹顶、V形肋和二级结构）以及不同类型的鳞片在理解该属的进化和系统发育方面的相对重要性却鲜为人知。在本研究中，我们调查了19株（18个物种）马洛莫纳斯（18株来自韩国生境）的鳞片和刚毛超微结构，以及三个基因的序列。这些分离株代表了19个组中的9个。测定了19株马洛莫纳斯分离株和四个外类群的核小亚基和大亚基核糖体DNA以及核酮糖-1,5-二磷酸羧化酶（rbcL）基因的质体大亚基的序列。对数据进行的贝叶斯分析和最大似然（ML）分析表明，马洛莫纳斯属由两个得到有力支持的进化枝组成。孟加拉马洛莫纳斯（E. Takah. et T. Hayak.）Siver et A. P. Wolfe位于第一个进化枝的基部，该进化枝包括来自扁平组和平行刺组的分类群，这两个组的鳞片盾上都没有V形肋。我们的结果表明，扁平组和平行刺组应该合并。第二个进化枝以无纹马洛莫纳斯Penard和斑点马洛莫纳斯Korshikov为基部，包含来自马洛莫纳斯组、条纹组、顶饰组、环纹组、具环组、斑点组和无纹组的分类群，所有这些组的鳞片上都有V形肋或发育良好的边缘肋。马洛莫纳斯属和条纹组之间的姐妹关系得到有力支持，但其余组之间的相互关系未得到解决，可能是由于纳入的物种太少。我们的结果表明，目前马洛莫纳斯属在组水平上的分类需要一些修订。未来的分析需要增加更多物种。
