Biosystematic studies on the genus Heloniopsis (Melanthiaceae) I. Phylogeny inferred from plastid DNA sequences and taxonomic implications

Abstract

Based on a combined dataset of plastid DNA sequences (atpB‐rbcL, trnG, trnL‐trnL‐trnF, trnK 5' intron and matK) from 60 individuals, we conducted parsimony and likelihood analyses to clarify the phylogenetic relationships among the six species and three varieties that are commonly recognised in Heloniopsis, in addition to the related genera Ypsilandra and Helonias, using Chamaelirium and Chionographis as an outgroup. According to the single most parsimonious tree, which was identical to the maximum‐likelihood tree in topology, Helonias, Ypsilandra and Heloniopsis are all monophyletic with 100% bootstrap support (BS). In Heloniopsis, there are two highly supported clades (BS 94–97%): a clade of Korean species and a clade of Japanese and Taiwanese species. The latter clade comprised the following four subclades (BS 99–100%): 1) H. orientalis var. orientalis, 2) H. orientalis var. breviscapa and var. flavida, 3) H. kawanoi and 4) H. leucantha and H. umbellata. Because subclades 1 and 2 did not form a monophyletic group, and do show clear morphological differences – including nectary position, nectary‐sac structure and leaf margin undulation – they should be distinguished at the species level: H. orientalis for subclade 1 and H. breviscapa for subclade 2. In subclade 2, neither var. breviscapa nor var. flavida was monophyletic; instead, var. breviscapa plus var. flavida (thick‐leaved entity) was monophyletic (BS 62–63%) and var. flavida (thin‐leaved entity) was monophyletic (BS 86–87%). As var. breviscapa and var. flavida (thick‐leaved entity) share basally ± pinkish wide tepals and dark‐coloured thick leaves, in contrast to var. flavida (thin‐leaved entity), which has completely white narrow tepals and light‐coloured thin leaves, the two varieties should may be kept distinct after the merge of var. flavida (thick‐leaved entity) with var. breviscapa.