Department of Botany and Plants Sciences, University of California, Riverside, California 92521 USA;
Am J Bot. 2005 Dec;92(12):2072-85. doi: 10.3732/ajb.92.12.2072.
Determining accurate phylogenetic relationships among the members of the woody Sonchus alliance presents challenges because of an insufficient level of molecular variation and the convergent evolution of similar morphological traits in island settings. To obtain a better resolved phylogeny and to test the potential role of hybridization and introgression, we sequenced all members of the alliance with multiple populations for the ITS of nrDNA and over 4000 base pairs of coding and noncoding regions of cpDNA. The cpDNA phylogeny is not well resolved in the core members of the alliance (i.e., subg. Dendrosonchus and genus Taeckholmia), but like the ITS tree, it has identified basal lineages of monotypic genera. The cpDNA data set was not significantly different from that of ITS, and subsequent combined analysis provided a better resolved and supported phylogeny within the alliance. The combined ML tree identified the same basal lineages, suggested nonmonophyly of Dendrosonchus and Taeckholmia, and did not support either Boulos' or Aldridge's infrasubgeneric classification system. Assessment of the role of hybridization and introgression was limited due to poor resolution in the cpDNA phylogeny. The combined analysis supports a Gran Canaria origin for the alliance and two subsequent long distance dispersal events to Madeira and Cape Verde islands.
确定木质的 Sonchus 联盟成员之间准确的系统发育关系具有挑战性，因为分子变异程度不足，以及岛屿环境中相似形态特征的趋同进化。为了获得更好的系统发育分辨率，并检验杂交和基因渗入的潜在作用，我们对联盟的所有成员进行了测序，包括 nrDNA 的 ITS、超过 4000 个碱基对的 cpDNA 编码区和非编码区。cpDNA 系统发育在联盟的核心成员（即亚属 Dendrosonchus 和属 Taeckholmia）中没有得到很好的解决，但与 ITS 树一样，它确定了单种属的基础谱系。cpDNA 数据集与 ITS 没有显著差异，随后的联合分析在联盟内提供了一个分辨率更高、支持度更强的系统发育。联合 ML 树确定了相同的基础谱系，暗示 Dendrosonchus 和 Taeckholmia 的非单系性，并且不支持 Boulos 或 Aldridge 的亚属分类系统。由于 cpDNA 系统发育分辨率较差，对杂交和基因渗入作用的评估受到限制。联合分析支持联盟起源于大加那利岛，并随后发生了两次远距离扩散事件，到达马德拉群岛和佛得角群岛。
