Stenophora

Hsu, K. - M., Tsai, J. - L., Chen, M. - Y., Ku, H. - M. & Liu, S. - C., 2013, Molecular phylogeny of Dioscorea (Dioscoreaceae) in East and Southeast Asia, Blumea 58 (1), pp. 21-27 : 25

The Stenophora clade

As shown in Fig. 1 , all Dioscorea species formed a monophyletic group with two distinct, strongly supported clades (clade A and B). This confirms that D. sect. Stenophora (clade A) is sister to the rest of Dioscorea (clade B) in the systematics of the genus as reported in Wilkin et al. (2005). Many ancestral characteristics of the genus are also present in D. sect. Stenophora including rhizome, diploid chromosome number and single pollen aperture ( Pei et al.1979, Chin et al.1985, Schols et al. 2003). Because its fossil record is the earliest of the genus Dioscorea , sect. Stenophora has been proposed as the oldest section in Dioscorea ( Burkill 1960) .

Furthermore, D. collettii was reported as a Sino-Himalayan species in Thapyai et al. (2005). Burkill (1960) had distinguished an additional species from D. collettii , which he called D. hypoglauca . However, in the most recent treatment of this species, Ding & Gilbert (2000) defined D. hypoglauca as a variety of D. collettii , D. collettii var. hypoglauca . These two taxa exhibit continuous morphological variations and show sympatric distribution in China. Gao et al. (2008) suggested that D. collettii var. collettii and D. collettii var. hypoglauca were sister to each other with only weak support. In this study, these two taxa were also sister to each other, but with strong support ( Fig. 1 node 7). In addition, the specimens of D. collettii var. collettii sampled from Taiwan and Lanyu Island showed three stable transversions within cpDNA trnL-F and matK regions. Thus, denser sampling is required to evaluate the intraspecific classification of D. collettii var. collettii in the future.

Figures

Fig. 1 Bayesian tree of Dioscorea specimens reconstructed with combined chloroplast genome trnL-F, matK, rbcL and atpB-rbcL DNA sequences. Statisti- cal supports for each node (node numbers on the branches of the tree) in NJ, MP and BI analyses is shown in the table on the left. An asterisk (*) indicates a node value <50 %.