Biosystematic studies on the family Nartheciaceae (Dioscoreales) I. Phylogenetic relationships, character evolution and taxonomic re-examination

摘要

Generally, the family Nartheciaceae is thought to comprise Narthecium (7 spp.), Nietneria (2 spp.), Lophiola (2 spp.), Metanarthecium (1 sp.) and Aletris (ca. 30 spp.), but the taxonomy is quite controversial. To clarify nartheciaceous taxonomy, we conducted molecular phylogenetic analyses of four regions (atpB–rbcL, trnL, trnL–F and 18S rDNA; 4,048 bp in total) using 38 samples, and five regions (plus trnK; 6,337 bp in total) using 26 samples. The four- and five-region analyses indicated that Metanarthecium was the first to diverge from the Nartheciaceae, followed successively by Aletris, Lophiola, Nietneria and Narthecium. Metanarthecium has sometimes been considered congeneric with Aletris, but should be recognised as an independent genus. Aletris foliata, A. fauriei, A. formosana, A. glabra and A. sikkimensis have sometimes been considered conspecific, but this conclusion is not robustly supported. Originally, bifacial leaves and septal nectaries were present in the Nartheciaceae, but the leaves evolved to become unifacial and the septal nectaries were lost within the family, i.e. at the lineage of Narthecium, Nietneria and Lophiola. The ovary frequently shifted from the superior position to somewhat lower positions, and vice versa, in the Nartheciaceae.