Department of Biology, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3 Canada;
Am J Bot. 2005 Oct;92(10):1749-58. doi: 10.3732/ajb.92.10.1749.
Turnera provides a useful system for exploring two significant evolutionary phenomena-shifts in breeding system (distyly vs. homostyly) and the evolution of polyploids. To explore these, the first molecular phylogeny of Turnera was constructed using sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA for 37 taxa. We attempted to resolve the origins of allopolyploid species using single-strand conformation polymorphism and sequencing of homeologous copies of ITS. Two allohexaploid species possessed putative ITS homeologues (T. velutina and T. orientalis). A phylogenetic analysis to identify progenitors contributing to the origins of these polyploids was unsuccessful, possibly as a result of concerted evolution of ITS. Breeding system evolution was mapped onto the phylogeny assuming distyly to be ancestral in Turnera. Self-compatible homostyly appears to have arisen independently at least three times in Turnera; however, we were not able to determine whether there have been independent origins of homostyly among hexaploid species in series Turnera. Our phylogenetic analyses suggest that series Turnera is monophyletic. Neither series Microphyllae nor Anomalae, however, appear to be monophyletic. Future taxonomic revisions may require new circumscriptions of these latter series.
特纳拉（Turnera）为探索两个重要的进化现象提供了一个有用的系统——繁殖系统（二型花柱与同型花柱）的转变，以及多倍体的进化。为了探索这些现象，我们使用核核糖体 DNA 的内部转录间隔区（ITS）序列构建了特纳拉的第一个分子系统发育，涉及 37 个分类群。我们试图使用单链构象多态性和 ITS 同源拷贝的测序来解决异源多倍体物种的起源问题。两个异源六倍体物种拥有假定的 ITS 同源物（T. velutina 和 T. orientalis）。一项旨在识别多倍体起源祖先的系统发育分析没有成功，这可能是由于 ITS 的协同进化。假设二型花柱在特纳拉中是祖先的，我们将繁殖系统的进化映射到系统发育上。自交同型花柱似乎至少在特纳拉中独立出现了三次；然而，我们无法确定在同一系列的六倍体物种中同型花柱是否有独立的起源。我们的系统发育分析表明，特纳拉系列是单系的。然而，小叶片系列和异常系列似乎都不是单系的。未来的分类修订可能需要对这些系列进行新的定义。
