Sageretia cordiformis (Y.L.Chen & P.K.Chou) Yi Yang, H.Sun & H.Peng, comb. &, 2021

Yang, Yi, Peng, Hua & Sun, Hang, 2021, Taxonomic revision of Sageretia (Rhamnaceae) from China I: identities of S. lucida, S. thea var. cordiformis and S. yunlongensis, with the description of a new species S. ellipsoidea, PhytoKeys 179, pp. 13-28 : 13

Sageretia cordiformis (Y.L.Chen & P.K.Chou) Yi Yang, H.Sun & H.Peng, comb. & stat. nov.: xin ye que mei teng (心叶雀梅藤) Figs 3C, D , 4A, B

S. thea var. cordiformis Y.L.Chen & P.K.Chou in Bull. Bot. Lab. North-East. Forest. Inst. 5: 74. 1979. Basionym.

Type material.

China. Yunnan: Xishuangbanna, Mengla County, 730 m, 28 Dec 1958, W.T. Wang 10496 (holotype KUN [1207932]; isotype KUN [1207933]).

Description.

Evergreen shrubs. Branches usually alternate, armed, glabrous to puberulent; second- to fourth-year branches brown. Leaves alternate or subopposite; petioles 1-3 mm, leaf blades leathery, shiny, glabrous, cordate to ovate-orbicular, 1-3 × 0.8-2 cm, lateral veins 2-3 pairs, flat abaxially, impressed adaxially, base cordate or subcordate, margin crenate, apex obtuse or rounded. Inflorescences spicate or spicate-paniculate; rachises 1.5-5 (-10) cm. Flowers sessile; sepals triangular-ovate; petals clawed; stamens as long as petals. Drupes subglobose, ca. 5-6 mm in diam., from green to red and finally turn black, base with persistently reflexed calyx; pyrenes 2-3, emarginate at both ends, asymmetrical.

Phenology.

Flowering in September; ripe fruits from December to January of the following year.

Distribution and habitat.

The species is distributed in China (southwestern Yunnan; Fig. 2 ). It grows in thickets on tropical limestone mountains at elevation from 700 to 1100 m.

Note.

In Flora Yunnanica, Fan (2006) reduced Sageretia thea var. cordiformis to the synonym of S. cordifolia (Fig. 3A, B ) with no justification given. S. cordifolia occurs in Laos (Pakson) and factually resembles S. thea var thea . However, S. thea var. cordiformis and S. cordifolia differ in petiole length (1-3 mm in former vs. 4-8 mm in latter), leaf blade shape (cordate to ovate-orbicular vs. ovate-oblong to ovate-lanceolate) and size (1-3 × 0.8-2 cm vs. 3.5-6 × 1.5-3 cm), and number of lateral veins (2-3 pairs vs. 3-5 pairs) (Table 1 ). Hence, we disagree with Fan’s treatment.

Based on specimen examination and our field observations, S. thea var. cordiformis and the type variety (Fig. 3E, F , Fig. 4C, D ) differ in petiole length (1-3 mm in S. thea var. cordiformis vs. 2-7 mm in type variety), leaf blade texture (leathery vs. papery), and number of lateral veins (2-3 pairs vs. 3-5 (-7) pairs). In fact, Chen and Chou (1979) had clearly mentioned the sharp morphological distinctions between S. thea var. cordiformis and the type variety in the protologue. Furthermore, the results of molecular phylogenetic analyses based on five loci (ITS, ETS, psb A- trn H, pet A- psb J and trn L- trn F) in Yang et al. (2019) indicated the independent species status of S. thea var. cordiformis splitting from the type variety. In their study, S. thea var. cordiformis , S. pycnophylla C.K.Schneid. and S. yilinii G.S.Fan & S.K.Chen form a clade, while S. thea var. thea is in a highly supported clade with S. subcaudata C.K.Schneid. and S. rugosa . Considering the broad discrepancies between S. thea var. cordiformis and S. thea var. thea in morphology and molecular phylogeny, we raise the former to S. cordiformis .

Specimens of Sageretia cordifolia examined.

Laos. Pakson, 1200 m, Nov 1938, E. Poilane 28562 (holotype P [01818865]; isotypes P [P01818866, P01818867, P06765093]).

Additional specimens of Sageretia cordiformis examined.

China. Yunnan: Mengla County, 25 Sept 1961, Y.H. Li 3588 (KUN); 1200 m, 24 Nov 1975, Y.H. Li 20033 (HITBC); 1000 m, 9 Sept 1959, S.C. Pei 10046 (HITBC); 10 Sept 2004, S.S. Zhou 2084 (PE); ca. 1000 m, 21 Dec 2015, Y. Yang & Z. Chen xsbn03 (KUN); ca. 1000 m, 24 Dec 2016, Y. Yang & L.S. Qian OYY001 (KUN).

Figures

Figure 2. Distribution of Rhamnus nigricans, Sageretia cordiformis, S. ellipsoidea, and S. lucida. The sites were obtained from the specimen records, our field investigations and photo information in CFH and PPBC.

Figure 3. Type specimens of Sageretia cordifolia, S. cordiformis and S. thea A, B isotypes of S. cordifolia (A: P [P 01818867]; B: P [06765093]) C holotype of S. cordiformis (KUN [1207932]) D isotype of S. cordiformis (KUN [1207933]) E, F isotypes of S. thea (E: S [S 11 - 12914]; F: LD [1749752]). A, B and E, F obtained from GBIF, C, D from NOI (https: // noi. link /).

Figure 4. Field photos of Sageretia cordiformis (A, B) and S. thea (C, D) A and C habit B and D fruiting branch and leaf blades A-C photographed by Y. Yang, D by X. X. Zhu.