Order level differences in the structure of partial LSU across demosponges (Porifera): new insights into an old taxon
Order level differences in the structure of partial LSU across demosponges (Porifera): new insights into an old taxon
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DOI：
10.1016/j.ympev.2004.02.014
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发表时间：
2004-07-01
影响因子：
4.1
通讯作者：
van Soest, RWM
中科院分区：
文献类型：
--
作者：
Erpenbeck, D;McCormack, GP;van Soest, RWM
海绵的形态系统学常常因复杂性状的缺乏或不明确而受到阻碍。一个典型的例子是海绵海绵纲（demosponge order）Halichondrida及其家族（sensu货车索斯特等人，1990），缺乏明确统一的synapomorphies和经常被定义为非独特的形态特征combinations.Molecular标记是强大的系统发育工具，在大多数后生动物，但仍然没有充分建立海绵。核核糖体大亚基（LSU）是后生动物中常见的系统发育标记，其变异最大的区域位于后扩张节或后扩张节。真核LSU基因具有12个这样的结构域，其中D2、D3和D8是最好表征的（纳恩等人，1996年）。它们被更保守的核蛋白或核蛋白片段互换，维持它们的特定功能。D2和D3结构域的二级结构被认为是保守的（Michot et al.，1990;纳恩等人，1996）并已用于高等海绵分类群的系统发育分析（D1-D2：例如，Chombard和Boury-Esnault，1999; Chombard等人，1997; Lafay等人，1992; D3：Alvarez等人，2000; D3-D5：McCormack和Kelly，2002; McCormack等人，2002年）。在分子系统学研究中，可变性状位置的正确排列是至关重要的一步。rRNA折叠的结构信息有助于使比对中的模糊性最小化（例如，Alvarez等人，2000年），并将保留系统发育序列信息。
Morphological systematics of sponges is often hampered by the lack or the ambiguous nature of complex characters. A typical example is the demosponge order Halichondrida and its families (sensu van Soest et al., 1990) that lack clearly uniting synapomorphies and are frequently defined by non-unique morphological character combinations.Molecular markers are powerful phylogenetic tools in most metazoans but are still not sufficiently established for sponges. The large nuclear ribosomal subunit (LSU) is a popular phylogenetic marker in Metazoa with its most variable regions located in the ÔexpansionÕ or ÔDÕ segments. The eukaryotic LSU gene harbours 12 such domains of which D2, D3, and D8 are the best characterized (Nunn et al., 1996). They are interchanged by the more conservative ÔcoreÕ or ÔCÕ segments, which maintain their specific function. The secondary structures of the D2 and D3 domains are considered to be conservative (Michot et al., 1990; Nunn et al., 1996) and have been used for phylogenetic analyses of higher sponge taxa (D1–D2: eg, Chombard and Boury-Esnault, 1999; Chombard et al., 1997; Lafay et al., 1992; D3: Alvarez et al., 2000; D3–D5: McCormack and Kelly, 2002; McCormack et al., 2002). The correct alignment of variable character positions is a crucial step in molecular systematics. Structural information of rRNA folding is helpful for minimizing ambiguities in alignments (eg, Alvarez et al., 2000) and will preserve phylogenetic sequence information.