Spatholobus discolor

Song, Zhuqiu, Yao, Gang, Jiang, Kaiwen, Liao, Junjie & Xu, Dongxian, 2021, Spatholobus discolor, a new synonym of Craspedolobium unijugum (Fabaceae), Phytotaxa 489 (3), pp. 263-274 : 267

Identity of Spatholobus discolor

Spatholobus discolor was published by Wei (1985) based on one flowering gathering (De-Ding Tao 91, KUN) from Lüchun Hsien, Yunnan Province, China. But no more specimens were ever found since the species was described, which results in the lack of fruit description in literature ( Ridder-Numan 1992, Wei 1994, Li & Wang 2006, Chen et al. 2010). We examined the holotype (KUN1208115, Fig. 2A ) and found that this species was recorded by the collector to be common in open shrubs vegetation, which seems to be inconsistent with its rare records of specimens. Though the holotype was flowering, the collector recorded the species has brown winged fruits ( Fig. 2A ). Furthermore, we traced two isotypes of the name, which are currently placed under the genus Craspedolobium . One isotype (KUN0623267) has many unopen flowers and was identified as “ Spatholobus roxburghii var. denudatus Baker ” by Heng-Chang Wang in 2001 and as “ Craspedolobium schochii ” by Bo Pan in 2014, while the other (HITBC0011543, Fig. 2B, 2D ) has some immature fruits densely covered with brown tomentose hairs and was determinated as “ Craspedolobium schochii Harms ” by Chong-Jiang Zhao in 2004. It is clear that both isotypes were not examined by the author of the scientific name. Besides, we traced one fruiting gathering that collected at the same locality on same collection date by the same collector as holotype (De-Ding Tao 117, Fig. 2C, 2E ). This fruit gathering appears to be similar with the type specimens of Spatholobus discolor in the habitat and many characters, but it has brown tomentose, winged pods, which is consistent with the records in the holotype. This fruit collection was correctly identified as “ Craspedolobium schochii ” ( Fig. 2C ). Therefore, observations of previous authors on these important specimens including its types showed that Spatholobus discolor is likely conspecific with Craspedolobium unijugum .

The genus Spatholobus comprises about 29 or 30 species distributed in Southeast Asia ( Ridder-Numan 1992, Schrire 2005, Chen et al. 2010). Morphologically, Spatholobus is consistent with Craspedolobium in many morphological characters, including the woody scandent habit, trifoliolate leaves, persistent stipels, pseudopanicles, and diadelphous stamens. However, these two genera are quite different in the number of ovules and position of the seeds in the fruit ( Geesink 1984, Lôc 1998). Spatholobus has 2 (very rarely 3–4) ovules per ovary and samaroid pods with only one seed located at a narrower apical part, while Craspedolobium has 5–8 ovules and marginally winged pods with several seeds scattered along the upper suture ( Geesink 1984). In the revision of the monotypic genus Craspedolobium, Lôc (1998) pointed out seven important characteristic features of this taxon, including trifoliolate leaves with asymmetric lateral leaflets, axillary and terminal pseudoracemes, calyx lobes with hairs on both sides, diadelphous stamens, 5–8 ovules per ovary, flat and dehiscent pod with the winged suture, and 2–5 seeds per pod. Furthermore, the observations on specimens and living plants showed that Craspedolobium has branchlets with numerous lenticels, the upper surface of leaflets often turning black when dry, a minute tip of leaflet, the longest calyx lobe forming a cover in bud, and a relatively long beak at the apex of the pod ( Fig. 3 ), which are also five very useful features for recognizing this taxon, especially when the materials lacking ripe fruits. In fact, we found all these features except for the ripe fruit character in the type specimens of Spatholobus discolor ( Fig. 2 ). Additionally, results from the examination of literature also showed that there are no clear differences between Spatholobus discolor and Craspedolobium unijugum ( Table 1). Therefore, it could be concluded that Spatholobus discolor is identical with Craspedolobium unijugum , and the former name should be treated as a new synonym of the latter.

Figures

FIGURE 2. Craspedolobium unijugum (Gagnep.) Z. Wei & Pedley. A. holotype of Spatholobus discolor C. F. Wei (De-Ding Tao 91, KUN1208115); B, D, E & F. isotype of Spatholobus discolor C. F. Wei (HITBC0011543), D showing the branchlet with numerous lenticels, E showing the minute tip of leaflet (red arrow), F showing the immature seeds; C & G. fruiting specimen (De-Ding Tao 117, HITBC0011535). Scale bar = 1 cm.

FIGURE 3. Craspedolobium unijugum (Gagnep.) Z. Wei & Pedley. A. habit; B. flowering branchlets; C. trifoliolate leaf as well as the minute tips and variation of apex of terminal leaflets; D. flowering and fruiting branchlets; E. branchlet with numerous lenticels; F. part of inflorescence with unopen flowers; G. immature pods; H. immature green pods, showing the narrow wing on the upper suture as well as four well developed and four abortive seeds; I. brown and dehiscent pods when mature. Scale bar = 1 cm.