Makino Herbarium, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan.
Mol Phylogenet Evol. 2013 Sep;68(3):699-708. doi: 10.1016/j.ympev.2013.04.019. Epub 2013 Apr 29.
Gynochthodes boninensis is a woody climber endemic to the Bonin Islands, Japan. It is characterized by an androdioecious sexual system, which is rare in angiosperms. We conducted a molecular phylogenetic analysis of 29 taxa including 61 samples from the tribe Morindeae to elucidate the geographical origin of G. boninensis by determining its progenitor species. We also investigated evolutionary transitions among different sexual systems within this plant group. The combined ETS, ITS, and trnT-F sequence data showed that G. boninensis formed a monophyletic group, but it did not form a clade with G. umbellata, which was treated as the same species, whereas it formed a clade with G. parvifolia, which is distributed in southeastern Asia. This suggests that G. boninensis evolved independently from G. umbellata, and probably originated from a progenitor native to southeastern Asia. In the clade composed of the three species of G. boninensis, G. parvifolia, and G. umbellata, only G. boninensis is androdioecious, whereas the others are dioecious. Thus, the androdioecious sexual system of G. boninensis may have evolved from dioecy.
野桐是原产于日本小笠原群岛的木质藤本植物。它的雌雄异株的性系统是被子植物中罕见的。我们对包括来自 Morindeae 族的 61 个样本在内的 29 个分类群进行了分子系统发育分析，通过确定其祖先物种来阐明野桐的地理起源。我们还研究了该植物类群中不同性别系统之间的进化转变。ETS、ITS 和 trnT-F 序列的联合数据表明，野桐形成一个单系群，但它没有与被视为同一物种的 G. umbellata 形成一个分支，而是与分布在东南亚的 G. parvifolia 形成一个分支。这表明，野桐是从 G. umbellata 中独立进化而来的，可能起源于东南亚的一个祖先生长地。在由三个野桐种、G. parvifolia 和 G. umbellata 组成的分支中，只有野桐是雌雄同体的，而其他两种是雌雄异株的。因此，野桐的雌雄同体性系统可能是从雌雄异株进化而来的。
