Institute of Biology, Evolutionary Botany, University of Neuchâtel, Rue Emile-Argand 11, 2009 Neuchâtel, Switzerland.
Mol Phylogenet Evol. 2009 Dec;53(3):734-48. doi: 10.1016/j.ympev.2009.07.025. Epub 2009 Jul 29.
Within the Gentianaceae-Exaceae, the most species-rich genus Sebaea has received very little attention in terms of phylogenetic or karyological investigations. As a result, the exact number of species remains vague and the relationships with the other members of the Exaceae poorly understood. In this paper, we provide the first comprehensive phylogeny of the Exaceae including most Sebaea species known so far based on four cpDNA sequence regions. In addition, morphological and karyological characters were mapped on the inferred phylogenetic trees to detect possible non-molecular synapomorphies. Our results reveal the paraphyly of Sebaea and highlight new generic relationships within the Exaceae. Sebaea pusilla (lineage S1--Lagenias) forms a highly supported and early diverging clade with Sebaeas.str. (clade S2 -Sebaea). A third clade of the former Sebaea s.l. (clade S3--Exochaenium) contains exclusively tropical African species, and is sister with a large clade containing all the remaining genera of Exaceae. Within the latter, the proposed sister relationships between the recently described Klackenbergia and Ornichia are highly supported. Optimization of several morphological characters onto the inferred phylogenetic trees reveals several synapomorphies for most highly supported clades. In particular, lineage S1 (Lagenias) is supported by medifixed anthers that are inserted at the base of the corolla tube and cubical seeds with polygonal testa cells; clade S2 (Sebaea) is supported by both the presence of secondary stigmas along the style and ridged seeds with rectangular testa cells arranged in row; clade S3 (Exochaenium) is supported by its particular gynoecium (stylar polymorphism and clavate, papillose stigma). Finally, karyological reconstructions suggest a basal number of x=7 for the Exaceae and several episodes of dysploidy leading to x=8 and 9.
在龙胆科-Exaceae 中，Sebaea 是物种最丰富的属之一，但在系统发育或核型研究方面几乎没有受到关注。因此，确切的物种数量仍然模糊不清，与 Exaceae 其他成员的关系也知之甚少。在本文中，我们提供了第一个基于四个 cpDNA 序列区域的 Exaceae 包括迄今为止已知的大多数 Sebaea 物种的综合系统发育。此外，形态学和核型特征被映射到推断的系统发育树上，以检测可能的非分子同形特征。我们的结果揭示了 Sebaea 的并系性，并突出了 Exaceae 内部的新属关系。Sebaea pusilla（谱系 S1--Lagenias）与 Sebaeas.str.（谱系 S2 -Sebaea）形成一个高度支持的早期分支。前 Sebaea s.l.的第三个分支（谱系 S3--Exochaenium）仅包含热带非洲物种，与包含 Exaceae 所有剩余属的大分支并列。在后一个分支中，最近描述的 Klackenbergia 和 Ornichia 之间的拟议姐妹关系得到了高度支持。推断的系统发育树上几个形态特征的优化揭示了大多数高度支持的分支的几个同形特征。特别是，谱系 S1（Lagenias）由中着药的花药支持，这些花药位于花冠管的基部，以及具有多边形种皮细胞的立方种子；谱系 S2（Sebaea）由沿花柱存在次生柱头和具脊种子支持，这些种子具有矩形种皮细胞排列成排；谱系 S3（Exochaenium）由其特殊的雌蕊支持（花柱多态性和棍棒状、乳突状柱头）。最后，核型重建表明 Exaceae 的基数为 x=7，并且发生了几次染色体数目异常，导致 x=8 和 9。
