Hylodesmum

Li, Huai-Cheng, Zhao, Xue-Li, Gao, Xin-Fen & Xu, Bo, 2019, Molecular phylogeny of the genus Hylodesmum (Fabaceae), Phytotaxa 403 (3), pp. 221-229 : 224

Systematics of Hylodesmum

Traditionally, the taxa belonging to Hylodesmum are divided into two sections, D. sect. Podocarpium and D. sect. Repanda ( Ohashi 1973, Yang & Huang 1995). Morphologically, species of D. sect. Podocarpium are characterized by calyx lobes that are much shorter than the tubes, whereas those of D. sect. Repanda are not shorter than the tubes. However, neither the traditionally defined D. sect. Podocarpium nor D. sect. Repanda within the genus was supported as monophyletic from the ITS analyses and combined ITS and chloroplast dataset analyses.

The D. sect. Repanda defined by Ohashi (1973) consists of three species, H. longipes ( Franchet 1889: 179) H.Ohashi & R.R.Mill (2000: 179) , H. repandum , and H. williamsii (H. Ohashi 1973: 163) H.Ohashi & R.R.Mill (2000: 186) . In all our tree topologies, H. longipes and H. repandum diverged earliest and formed clades with high support values (in ITS tree, LB = 89%, PJ = 93%, and PP = 1; in combined chloroplast tree, LB = 96%, PJ = 97%, and PP = 1; in combined ITS and cpDNA tree, LB = 98%, PJ = 98%, and PP = 1). However, in all phylogenetic trees, H. williamsii was not grouped with the other two species of the same section but gathered with other species in the genus, which showed that the relationships between H. williamsii and the other two species under D. sect. Repanda may be not as close as originally thought. Morphologically, the apex of the keel of this species is sharp and beak-like, which obviously differs from other species in the genus. Hence, the taxonomic position of H. williamsii may need reevaluation and further studies are required. The D. sect. Podocarpium defined by Ohashi (1973) consisted of only five species, with many new species being published later. The present study suggests that it should include ten species based on the morphological characteristics. D. sect. Podocarpium is disjunctively distributed in East Asia and North America, with seven species distributed in Asia and three species distributed in eastern North America. Our discussion within the section will follow the groups defined by Isely (1951).