Bolus Herbarium, Department of Biological Sciences, University of Cape Town, 7701 Rondebosch, South Africa.
Mol Phylogenet Evol. 2013 Dec;69(3):1005-20. doi: 10.1016/j.ympev.2013.05.030. Epub 2013 Jun 22.
The Ruschieae is a large tribe of about 1600 species of succulent perennials. They form a major component of the arid parts of the Greater Cape Floristic Region, both in numbers of species and in their density of coverage. So far phylogenetic relationships within the tribe have been unresolved, largely through the paucity of variable molecular characters and this is ascribed to the tribe's recent and rapid radiation. Our phylogeny is based on 10 chloroplast gene regions and represents a nearly complete sampling of the 100 currently recognised genera of the Ruschieae. These chloroplast regions yielded relatively few phylogenetically informative characters, consequently providing only limited resolution in and poor support for many parts of the phylogeny. Nevertheless, for the first time, we provide well-supported evidence that taxa with mostly mesomorphic, often ephemeral leaves and weakly persistent fruits form a basal grade of lineages in the Ruschieae. These lineages subtend a large polytomy of taxa with almost exclusively xeromorphic, persistent leaves and strongly persisting fruits. Among the basal grade of lineages, those occurring within the winter-rainfall region typically shed their leaves or form (at least partly) a protective, dry sheath around the apical bud during the dry summer months, as a means of escaping the summer drought. This contrasts with taxa of the basal grade from outside the winter-rainfall region, in which the leaves persist. Our results show that, in both strongly and weakly persistent fruits, specialised characteristics of the fruit evolved repeatedly and so these structures are highly homoplasious. Perhaps as a consequence of repeated changes towards increased persistence and specialisation of leaves and fruits, several clades show little morphological cohesion. However, as in other groups in the Cape Flora, most clades in the Ruschieae represent regional groupings. Our analysis of sequences of the nuclear gene 'chloroplast-expressed glutamine synthetase' (ncpGS) revealed extensive paralogy within the Ruschieae, but found an intact reading frame in all its members. More data on the cytology of the Ruschieae is needed to evaluate whether the paralogy observed is due to gene duplication or polyploidy.
罗氏藻族是一个约有 1600 种肉质多年生植物的大族群。它们在数量和密度上构成了大开普花卉区干旱部分的主要组成部分。到目前为止，该族内的系统发育关系还没有得到解决，主要是由于可变分子特征的缺乏，这归因于该族最近的快速辐射。我们的系统发育基于 10 个叶绿体基因区域，代表了目前识别的罗氏藻族 100 个属中的近完整采样。这些叶绿体区域产生的系统发育信息特征相对较少，因此仅在系统发育的许多部分提供有限的分辨率和较差的支持。尽管如此，我们首次提供了充分支持的证据，表明主要具有中胚叶、通常是短暂的叶子和弱持久果实的类群形成罗氏藻族的基础等级。这些谱系在具有几乎完全旱生叶、持久果实的类群的大型多系性中处于亚基部。在基础等级的谱系中，那些发生在冬雨区的类群在旱季期间通常会脱落叶子或形成（至少部分）围绕顶芽的保护性、干燥鞘，以逃避夏季干旱。这与冬雨区以外的基础等级的类群形成对比，后者的叶子持续存在。我们的结果表明，在强持久和弱持久的果实中，果实的特殊特征反复进化，因此这些结构高度同形。也许由于反复朝着增加持久性和叶子和果实的特化而发生变化，几个分支表现出很少的形态凝聚力。然而，与开普植物群中的其他群体一样，罗氏藻族中的大多数分支代表区域分组。我们对核基因“叶绿体表达谷氨酰胺合成酶”（ncpGS）序列的分析揭示了罗氏藻族内广泛的平行现象，但在其所有成员中都发现了完整的阅读框。需要更多关于罗氏藻族细胞学的数据来评估观察到的平行现象是由于基因复制还是多倍体。
