Rhodiola daochengensis J.Q. Zhang et G.Y. Rao, 2015

Zhang, Jian-Qiang, Meng, Shi-Yong & Rao, Guang-Yuan, 2015, Two new species of Rhodiola (Crassulaceae) from the Qinghai-Tibetan Plateau, Phytotaxa 224 (2), pp. 159-172 : 167-168

Rhodiola daochengensis J.Q. Zhang et G.Y. Rao sp. nov. ( Figs. 3–4 )

Type: — CHINA. Sichuan: Daocheng Co., 3900 m, 8 August 2011, J. Q. Zhang et al. 110808-01 (holotype, PEY!). China. Sichuan: Xiangcheng Co. , 4805 m, 20 August 2013, S. Y. Meng et al. 13082012 ; 13082008 (paratype, PEY!)

Diagnosis: —Dioecious, stems and pedicel densely glandular-pubescent; caudex leaves triangular-ovate to very broadly triangular; flowering stems 1–3; stem leaves alternate, sessile, oblong-lanceolate, denticulate; leaf base cordate, amplexicaul; Inflorescences terminal, very compact; Follicles erect, usually with outcurved styles; Seeds oblong, winged, the testa brown, with longitudinal low ridges.

Description: —A perennial herb, dioecious, up to 50 cm high. Caudex nearly erect, robust, usually 1–3 cm across; apical part often short, branched and accrescent, crowned by the scaly radical-leaves. Scaly radical-leaves chartaceous, persistent, triangular-ovate to very broadly triangular with entire margin, acute-obtuse at the apex, 3–5 mm long, 3–6 mm wide, brown. Roots very slender. Flowering stems 1–3 from apex of each caudex branch, deciduous, 25–50(60) cm long, and 5–7 mm in diameter, erect, simple, terete, densely glandular-pubescent. Leaves alternate, loosely arranged throughout, ascending-spreading, sessile, spurless, thick herbaceous, flattish, yellowish green, oblong-lanceolate; long acuminate at the apex; round-shallowly cordate at the base; serrate along the margin; 3–20 mm long, 2.5–5 mm wide; glabrous on both surfaces, the costa ± raised beneath. Inflorescences terminal, very compact, umbel-like cyme, 2–7 cm long, 2–4.5 cm wide; inconspicuously bractates (♂) and scarcely bracteates (♀), bracts leafy, linear to linear-subulate, round (-acute) at the apex, less than 10–31 mm long and 2.5–5 mm wide. Flowers 5(6)-merous, no seen. Follicles 2.5–5 mm long, each carpel erect, usually with outcurved styles, 14–18 seeds each carpel. Seeds 0.7–1.1mm long, 0.3–0.4mm wide, oblong, winged, the testa brown, longitudinally lowly ridged. See Figs 3 and 4 .

Habitat: —Perennial herbaceous on humid but not pond mountain ridges with bushes together, half-way up the limestone mountains, 3900–4805 m.

Phenology: —Flowers no seen; fruits from August to October.

Distribution: —So far, it has been found one population (21 individuals) in Daocheng County while another population containing at least 19 individuals was found in Xiangcheng County, northwestern region of Sichuan, China. With extensive road construction, water conservancy construction and mineral development, massive habitats were destroyed. This new species is thought to be endemic to China.

Etymology: —This species was firstly found in the mountains behind the Daocheng town, Sichuan province, China.

Notes: —The new species R. daochengensis belongs to sect. Rhodiola due to its cymose inflorescences, unisexual flowers and sessile, serrate stem leaves. It shares close morphological affinities with R. kirilowii which supported by the ITS data ( Fig. 1 ) but differed from the latter in the morphology of leaves, stems, pedicels, and fruits ( Table 3). However, the cpDNA data showed that R. daochengensis is more closely related to R. serrata ( Fig. 2 ). Chloroplast capture (i.e., replacement of the cytoplasm of one species by that of another species through hybridization/introgression; Rieseberg and Soltis 1991; Soltis and Kuzoff 1995) is a likely explanation for the observed incongruence between nuclear and plastid DNA data in Rhodiola . Chloroplast capture could occur frequently in species with sympatric distribution and reproductive compatibility (Rieseberg et al. 1991). Considering both morphological and molecular data, we compared the morphological characters of R. daochengensis with both R. kirilowii and R. serrata ( Table 3). R. daochengensis differs from R. serrata in the form of stems and pedicels, leaf shape, and the base of leaves ( Table 3).

Figures

FIGURE 1. Bayesian tree of Rhodiola species based on the analysis of ITS sequences. Bayesian posterior probabilities (PP) and MP bootstrap (BP) values are shown above the branches (PP/BP). Hyphen (-) indicates bootstrap support<50.

FIGURE 2. Bayesian tree of Rhodiola species based on the analysis of three plastid markers. Bayesian posterior probabilities (PP) and MP bootstrap (BP) values are shown above the branches (PP/BP). Hyphen (-) indicates bootstrap support<50.

FIGURE 3. Rhodiola daochengensis. a. a female plant; b. a male plant; c. rhizome.

FIGURE 4. Rhodiola daochengensis. a. rhizome and flowering stem; b. flowering stem of a male plant; c. flowering stem of a female plant; d. longitudinal section of a follicle; e. follicles; f. seeds.