Ashworth Matt P, Lobban Christopher S, Witkowski Andrzej, Theriot Edward C, Sabir Meeshal J, Baeshen Mohammad N, Hajarah Nahid H, Baeshen Nabih A, Sabir Jamal S, Jansen Robert K
Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA.
Division of Natural Sciences, University of Guam, Mangilao, Guam, USA.
Protist. 2017 Feb;168(1):48-70. doi: 10.1016/j.protis.2016.11.001. Epub 2016 Nov 17.
Several lineages of raphe-bearing diatoms possess a "stauros," which is a transverse, usually thickened area free of pores across the center of the valve. It has been suggested that this structure has evolved several times across the raphid diatoms, but we have noticed similarities beyond the stauros between two marine genera-Craspedostauros and Staurotropis-in the structure of their pore occlusions. We have isolated, cultured and extracted DNA from several strains of both genera to infer the phylogenetic relationship between these taxa, as well as test the suggested relationship of Craspedostauros to Achnanthes and Mastogloia based on plastid morphology. DNA sequence data (nuclear-encoded rRNA SSU, plastid-encoded rbcL and psbC) suggest that, except for Mastogloia, these genera are closely-related, though not sister taxa. The DNA phylogeny also suggests that the Mastogloiales are not monophyletic, with clades containing Achnanthes and Craspedostauros sister to clades containing taxa in the Bacillariales. Using evidence from molecular and morphological data, we describe the following new taxa: Craspedostauros alyoubii and C. paradoxa from the Red Sea and Guam, respectively; Staurotropis khiyamii and S. americana from the Red Sea and the Gulf of Mexico, respectively; and Dreuhlago cuneata n. gen., n. sp. from Guam.
几个具有缝脊的硅藻谱系拥有一种“十字形结构”，它是一个横向的、通常加厚的区域，横跨瓣膜中心且无孔隙。有人提出这种结构在整个具缝硅藻中已经进化了好几次，但我们注意到两个海洋属——十字形藻属（Craspedostauros）和十字扭转藻属（Staurotropis）——在孔隙闭塞结构上除了十字形结构之外还有相似之处。我们从这两个属的几个菌株中进行了分离、培养并提取了DNA，以推断这些分类单元之间的系统发育关系，同时基于质体形态来检验十字形藻属与曲壳藻属（Achnanthes）和胸隔藻属（Mastogloia）之间的推测关系。DNA序列数据（核编码的rRNA SSU、质体编码的rbcL和psbC）表明，除了胸隔藻属之外，这些属密切相关，尽管不是姊妹分类单元。DNA系统发育也表明胸隔藻目不是单系的，包含曲壳藻属和十字形藻属的分支是包含硅藻目分类单元的分支的姊妹分支。利用分子和形态数据的证据，我们描述了以下新分类单元：分别来自红海和关岛的阿尤布十字形藻（Craspedostauros alyoubii）和奇异十字形藻（C. paradoxa）；分别来自红海和墨西哥湾的基亚姆十字扭转藻（Staurotropis khiyamii）和美洲十字扭转藻（S. americana）；以及来自关岛的楔形德氏藻（Dreuhlago cuneata），新属，新种。
