Integrative Taxonomy Supports Two New Species of Rhodiola (Crassulaceae) in Xizang, China

Abstract

The Qinghai–Tibet Plateau includes the Himalayas and Hengduan Mountains and is well known for its rich biodiversity. Evolutionary radiation is one of the main ways by which plants diversify in mountains, particularly the Qinghai–Tibet Plateau. It presents a large challenge to the classification of taxa that radiate quickly. One way to overcome these challenges is to continue conducting detailed field studies while integrating morphological and molecular evidence to classify these taxa. The aim of this research was to provide a case for the systematic study of the complex taxa Rhodiola, which rapidly radiate. During the field study, we found two unique variants of Rhodiola in an alpine dry meadow and beds of pebbles on beaches, respectively. We utilized a morphological principal component analysis, scanning electron microscopy and molecular phylogenetic analysis to propose two new species: Rhodiola wangii S.Y. Meng and Rhodiola namlingensis S.Y. Meng. R. wangii is similar to R. stapfii (Hamet) S.H. Fu, but it differs in having an intensely broad rhombus and alternate leaves, a distinct petiole, stamens gathered together and reflexed purple scales. R. namlingensis is similar to R. prainii (Hamet) H. Ohba, but it differs in its exerted alternate leaves, the presence of more than four leaves on the stem, thick leaf blades, an obovate to inverted triangle, and short petioles. The conservation status of these two species was also assessed.

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Citation: Meng, S.; Wang, Z.; Ye, L.
Integrative Taxonomy Supports Two
New Species of Rhodiola
(Crassulaceae) in Xizang, China.
Diversity 2022,14, 289. https://
doi.org/10.3390/d14040289
Academic Editors: Hong-Hu Meng
and Yi-Gang Song
Received: 23 February 2022
Accepted: 6 April 2022
Published: 12 April 2022
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diversity
Article
Integrative Taxonomy Supports Two New Species of Rhodiola
(Crassulaceae) in Xizang, China
Shiyong Meng * , Zimeng Wang and Lv Ye
School of Life Sciences, Peking University, Beijing 100871, China; xztswzm@126.com (Z.W.);
yelv_123@163.com (L.Y.)
*Correspondence: msy542702@pku.edu.cn
Abstract: The Qinghai–Tibet Plateau includes the Himalayas and Hengduan Mountains and is well
known for its rich biodiversity. Evolutionary radiation is one of the main ways by which plants
diversify in mountains, particularly the Qinghai–Tibet Plateau. It presents a large challenge to the
classification of taxa that radiate quickly. One way to overcome these challenges is to continue
conducting detailed field studies while integrating morphological and molecular evidence to classify
these taxa. The aim of this research was to provide a case for the systematic study of the complex taxa
Rhodiola, which rapidly radiate. During the field study, we found two unique variants of Rhodiola in
an alpine dry meadow and beds of pebbles on beaches, respectively. We utilized a morphological
principal component analysis, scanning electron microscopy and molecular phylogenetic analysis to
propose two new species: Rhodiola wangii S.Y. Meng and Rhodiola namlingensis S.Y. Meng. R. wangii is
similar to R. stapfii (Hamet) S.H. Fu, but it differs in having an intensely broad rhombus and alternate
leaves, a distinct petiole, stamens gathered together and reflexed purple scales. R. namlingensis is
similar to R. prainii (Hamet) H. Ohba, but it differs in its exerted alternate leaves, the presence of more
than four leaves on the stem, thick leaf blades, an obovate to inverted triangle, and short petioles.
The conservation status of these two species was also assessed.
Keywords: Xizang; Rhodiola namlingensis;Rhodiola wangii; new species; taxonomy; radiation
1. Introduction
The Qinghai–Tibet Plateau (QTP) and adjacent high-altitude areas contain more than
12,000 species of flowering plants, which renders it one of the areas of the world with the
highest richness of species and a high level of endemism because of its habitats, such as high
mountainous ranges, steep gorges, rocky outcrops, desert steppes and alpine meadows
among others [1,2].
Evolutionary radiation is one of the main ways by which plants diversify in mountains,
particularly the Qinghai–Tibet Plateau [
3
,
4
]. However, radiated taxa are often inconsistent
between molecular phylogenetic and morphological classifications [
5
,
6
]. It is possible that
these inconsistencies are caused by inadequate sampling or limited genomic sampling with
insufficient molecular markers. In addition, some morphological characters are homoge-
neous [
6
]. Therefore, it is essential to recruit more molecular markers while conducting
more field surveys to find valid characters and more types of variation. Several attempts
by different types of molecular markers have been made to define the species of these
genera [
7
–
9
], but the importance of field study has been neglected. However, hundreds of
new plant species in the Qinghai–Tibet Plateau have been described in recent years [
10
],
indicating that the surveys conducted so far are highly insufficient.
Rhodiola L. are members of the Crassulaceae DC., which includes more than
70 different
species that are primarily distributed throughout the alpine zone of the northern hemi-
sphere, particularly in the Qinghai–Tibet Plateau and adjacent high-altitude areas. Their
major characteristics include well-developed thick rhizomes and apical parts with scaly
Diversity 2022,14, 289. https://doi.org/10.3390/d14040289 https://www.mdpi.com/journal/diversity

Diversity 2022,14, 289 2 of 13
leaves [
11
–
13
]. Rhodiola species occupy many habitats. For example, R. yunnanensis (Franch.)
S.H. Fu, R. macrocarpa (Praeg.) S.H. Fu, and R. liciae (Hamet) S.H. Fu are distributed in
thickets at low-to-medium altitudes; R. sacra (Prain ex Hamet) S.H. Fu and R. bupleuroides
(Wall. ex Hook. f. et Thoms.) S.H. Fu grow in rocky outcrops at medium-to-high altitudes,
and R. coccinea (Royle) Borissova and R. crenulata (Hook. f. et Thoms.) H. Ohba occupy
mountain tops that exceed 4500 m. Rhodiola are highly diverse morphologically, and Fu
and Fu [
14
] divided the genus into eight sections with seven series based on morphological
studies. However, molecular phylogenetic research showed that only three of the eight
sections (Sect. Trifida Fu, Sect. Prainia H. Ohba, and Sect. Pseudorhodiola (Diels) H. Ohba)
can be considered monophyletic, while two important characters (dioecy and marcescent
flowering stems) evolved multiple times within Rhodiola [
15
]. Molecular dating analysis
showed that the primary diversification of Rhodiola occurred during two periods of the
QTP uplifts, at 15–6.5 mya and 5–1.8 mya ago [
15
]. Rapid diversification, simplicity and
the homogeneity of morphological characters lead to taxonomic difficulties in Rhodiola,
particularly in the delimitation of species [
16
]. Thus, further intensive studies are still
merited with more extensive sampling to clarify the systematic relationships of Rhodiola.
Our aim was to explore the diversity of Rhodiola in the Qinghai–Tibet Plateau and
define species by combining morphological and molecular evidence. An extensive study of
the systematic evolutionary biology research of Rhodiola in the wild has been conducted
since 2010, which has led to the publication of some new Rhodiola species [
17
]. Here, we pro-
pose two new species of Rhodiola that are distributed on the platform of the
Qinghai–Tibet
Plateau. One of them is distributed on the shores of the plateau valley, whereas the other
grows in the alpine dry meadow. These new species are very small and can easily avoid de-
tection. The discovery of these two new species will help to understand the rapid radiation
of Rhodiola in the Qinghai–Tibet Plateau.
2. Materials and Methods
2.1. Materials Collection and Field Investigation
Habitat plays an important role in the diversification of Rhodiola [
15
], and we took
great pains to record that habitat during field investigations. Samples of two putative new
species were collected in the field, including one from LhünzêCounty (one population,
28
◦
06
0
00
00
N, 91
◦
55
0
53
00
E) and another from Namling County (Namling 1: 30
◦
04
0
91
00
N,
89
◦
06
0
27
00
E; Namling 2: 29
◦
55
0
56
00
N, 89
◦
07
0
01
00
E). Their close relatives were also collected
from Xizang Province, China. The type specimens and other specimens of R. prainii and R.
stapfii were examined, and specimens of the other related taxa were obtained from herbaria
(CVH, K, PE) and examined for comparative research.
2.2. Morphological Analysis
Leaf characters play an important role in the definition of Rhodiola species [
16
], while the
flowers are morphologically simple. Thus, the morphological analysis is primarily based on
the leaf characters. To avoid the influence of artificiality and find key delimitation traits, we
used a principal component analysis (PCA) to perform statistical analyses on the traits. We
observed and measured the leaf traits and conducted the PCA using Origin 2020 (OriginLab
Corporation, Northampton, MA, USA). All the data were quantitative, including the leaf
length (L), leaf width (W), length of petiole (P), relative length of the petiole (B = P/L), the
distance between the widest part of blade and the base of petiole (H), relative width of the
petiole (K = M/W), relative length of the distance between the widest part of blade and base
of petiole (D = H/L) and the shape of the blade (S = W/L) (Figure S1).
2.3. Scanning Electron Microscopy (SEM) Analysis
Although Gontcharova et al. [
18
] showed that the seed coats of Rhodiola in the Russian
Far East vary considerably, they correspond to the features of gross morphology at the
species level. Thus, we conducted a scanning electron microscopy (SEM) analysis using a
Helios NanoLab G3 UC (Thermo Fisher, Waltham, MA, USA). First, seeds were directly

Diversity 2022,14, 289 3 of 13
fixed on the sample shuttle. Secondly, the sample was coated with gold using a vacuum
sputter coater. Finally, the sample was transferred to the stage of the sample room for
observation. The terminology of seed coat sculpturing and anatomy were those described
by Gontcharova et al. [
18
]. The sizes of seeds were measured using Photoshop CC 2018
(Adobe, San Jose, CA, USA).
2.4. Phylogenetic Analysis
DNA barcoding research showed that the nuclear ribosomal internal transcribed
spacer (ITS) was the best single-locus barcode, resolving 66% of the Rhodiola [
19
]. Thus, the
ITS regions were used as molecular markers. The DNA of the new species was extracted
and amplified by PCR as described by Zhang et al. [
17
]. The ITS sequences of 33 specimens
of Rhodiola were downloaded from NCBI along with two accessions of Phedimus, another
genus of the Crassulaceae, as outgroups. The GenBank accession numbers are shown in
Table S1.
Phylogenetic analyses were performed using Bayesian inference (BI) and maximum-
likelihood (ML) methods in PhyloSuite [
20
]. The ITS sequences were aligned with MAFFT
v. 7 [
21
] and manually checked in PhyloSuite [
20
]. The evolutionary models for the ML and
BI analyses were determined by ModelFinder [
22
] using the Akaike Information Criterion
(AIC). ML trees with 1000 bootstraps (BS) were produced using an IQ-tree [
23
]. BS analyses
were used to evaluate the support for individual clades with 5000 replicates. A BI analysis
was performed using MrBayes [
24
]. Four chains of the Markov Chain Monte Carlo (MCMC)
were run for 2,000,000 generations, sampling one tree every 100 generations, starting with
a random tree. The average standard deviation of the split frequencies was used to assess
the convergence of two runs. A majority rule (>50%) consensus tree was constructed after
removing the burn-in period samples (the first 25% of the sampled trees) and posterior
probabilities (PP) to estimate the robustness of the BI trees.
3. Results
3.1. Habitat
During the field investigation, we found that these two new species and similar ones
grow on alpine meadows, but the habitats can be differentiated from each other. The
Lhünzêpopulation grows on the soil slopes of alpine meadows that are relatively dry,
while R. stapfii grows in the moist parts of alpine meadows. The Namling populations
primarily grow on the beds of pebbles on beaches or in rock crevices on the shore of the
Xiangqu (Jiacuo Zangbo), which is one of the Yarlung Zangbo’s tributaries. In contrast, R.
prainii primarily grows on rocks or trees in the subtropical rain forest on the southern slope
of the Himalayas and the slope rocks on the plateau of the Qinghai–Tibet Plateau.
3.2. Morphological Analysis
Morphologically, the Lhünzêpopulation is closely related to R. stapfii. However,
several characters differentiate them. First, rhizomes of the Lhünzêpopulation are glossy,
while those of R. stapfii are enfolded by the remnants of old shoots. Secondly, flowering
stems with some leaves are alternate in the Lhünzêpopulation, whereas all four to six
pieces of the leaves are in whorls and on the apical part of the R. stapfii rhizomes. Third, the
leaves of Lhünzêpopulation have obvious petioles, while those of R. stapfii are very short or
sessile. Finally, the stamens of the Lhünzêpopulation are gathered together, and the scales
are purple and reflexed. In contrast, the stamens of R. stapfii do not gather together, and
the scales are white. A principal component analysis (PCA) based on the 8 qualitative leaf
traits revealed considerable variability among the 44 individuals considered in this study
(Figure 1A). The PC1 scores, which accounted for 48.9% of the total variation, showed very
high correlation with length of the leaf (L) and petiole, including the relative width of the
petiole (K = M/W) and relative length of the petiole (B = P/L). The scores of PC1 were also
highly correlated with other traits, such as shape of the blade (S = W/L), relative length of
the distance between the widest part of blade and base of petiole (D = H/L), and the length

Diversity 2022,14, 289 4 of 13
between the widest part of blade and base of petiole (H). The PC2 scores, which explained
31.8% of the total variation, were highly correlated with the width of the leaf (W), between
the widest part of blade and the base of petiole (H) and length of the leaf (L).
Figure 1.
Principal component analysis based on the leaf traits. (
A
) Lhünzêpopulation and Rhodiola
stapfii (Raymond-Hamet) S.H. Fu. (B)R. namlingensis S.Y. Meng and R. prainii (Hamet) H. Ohba.
A morphological analysis indicated that the Namling populations are similar to those
of R. prainii with flattened leaf blade and similar inflorescences and flower structures.
However, the plants can be differentiated by several characters. First, the Namling popula-
tions contain more developed flowering stems, while R. prainii contains short flowering
stems, which usually have only two nodes on the stem. Secondly, leaves on the stems in
Namling populations are alternate, while the leaves of R. prainii often have four whorls
at the top of stem. The lower part of the stem leaves is opposite and has a developed
pseudopetiole that is 1 to 3 cm long. Third, R. prainii flowers from July to August, while
the Namling populations flower from September to mid-October. The PCA based on the
eight quantitative traits revealed a considerable variability among the 47 individuals. The
first two PCs together explained 89.7% of the total variation (Figure 1B). The PC1 scores,
which accounted for 61.5% of the total variation, were showed very high correlation with
the length of the leaf (L), width of the leaf (W), length between the widest part of blade and
base of the petiole (H) and length of the petiole (P). The scores of PC2, which explained
28.2% of the total variation, were highly correlated with the relative width of the petiole
(K = M/W), relative length of the petiole (B = P/L) and relative length of the distance
between the widest part of blade and base of petiole (D = H/L).
3.3. SEM Analysis
The seeds of R. stapfii are triangular with a wing-like projection at the chalazal end,
920
µ
m long, and 400
µ
m wide (Figure 2A). The testa cells are morphologically uniform
or vary only slightly in their shape and are less regularly arranged. The outer periclinal
cell walls are flat and smooth, while the anticlinal cell walls are thickened and bulging
(Figure 2E). The cells are quadrangular and isodiametric, and the cell boundaries are well-
defined and curved. The outer periclinal cell wall is convex. The seeds of the Lhünzê
population are square and lack wing-like projections at the chalazal end, and they are
519
µ
m long and 324
µ
m wide (Figure 2B). The testa cells are not readily apparent and
have dense stripes in the outer periclinal wall (Figure 2F). The seeds of R. prainii are
similar to those of R. stapfii. They are triangular but small (761
µ
m long and 309
µ
m wide)
(Figure 2C,G). They lack a wing-like projection at the chalazal end, and the anticlinal cell
walls are thin and sunken. The outer periclinal cell wall is thickened and convex. The
seeds of Namling populations are oblong and lack a wing-like projection at the chalazal

Diversity 2022,14, 289 5 of 13
end, and they are 835
µ
m long and 203
µ
m wide (Figure 2D). The testa cells have obvious
longitudinal edges on the surface; the width between the longitudinal edges is 23.6
µ
m,
and there are obvious horizontal stripes in the depressions between the edges that extend
to the longitudinal edges, forming a regular pattern of orbital decoration. (Figure 2H).
Figure 2.
Scanning electron microscopy of four Rhodiola seeds. (
A
,
E
)R. stapfii (PEY0067558);
(
B
,
F
) Lhünzêpopulation (PEY0067593); (
C
,
G
)R. prainii (PEY0068682); (
D
,
H
) Namling population
(PEY0067596); (A–D) The shape of seeds; (E–H) Local magnification of the seed micromorphology.

Diversity 2022,14, 289 6 of 13
3.4. Molecular Analyses
Following the alignment, we obtained a matrix of 588 base pairs (bp) and selected SYM+G4
for the Bayesian and ML analyses (Figure S2). The 50% majority rule consensus tree of all the
post burn-in trees is shown in Figure 3with the Bayesian posterior probabilities (PPs).
Figure 3.
A Bayesian phylogenetic tree based on ITS sequences for the two new Rhodiola species
described and their close relatives. The topology of the maximum likelihood (ML) tree was highly
compatible with that of the Bayesian tree. Bayesian posterior probabilities (PPs: left) and bootstrap
support (BP: right) values (>50%) are shown above the branch.
The BI tree strongly supported the monophyly of Sect. Trifida, Sect. Prainia, and Sect.
Pseudorhodiola. The two samples of Namling populations from different sites are shown as a
distinct clade (Posterior Probability [PP] = 1.0, Bootstrap value [BP] = 100%). The Namling
populations formed a monophyletic clade with the species of Sect. Trifida and Sect. Prainia
(PP = 0.84, BP = 64) (Figure 3), whereas the Lhünzêpopulation formed a monophyletic
clade with R. smithii and R. humilis (PP = 0.70, BP = 62).
4. Discussion
This survey found that species of Rhodiola have spread to the dry soil slopes of alpine
meadow and beds of pebble beaches on the Qinghai–Tibet Plateau. It shows that Rhodiola
has occupied various habitats on the Qinghai–Tibet Plateau. The habitat reflects the
radiation of Rhodiola, which is consistent with the results of molecular systematics [15,25].
Seed micromorphology provides many characters that are potentially useful to identify
species and perform phylogenetic inference in the Crassulaceae [
26
–
28
]. However, there
has been little research on the seed coat micromorphology of Rhodiola [
18
]. In this study,
we conducted an SEM analysis of the seed coats of R. prainii,R. stapfii, and the Namling
and Lhünzêpopulations. The results show that the two morphological types of these four
species differed from those previously reported [
18
]. The surface ornamentation of the
seed coats of the Namling populations clearly differ from those of R. prainii, as do those
of the Lhünzêpopulation and R. stapfii. Thus, the seed coat characters of Rhodiola show

Diversity 2022,14, 289 7 of 13
considerable diversity and have some value in the delimitation of species. Thus, there
should be more focus on the seed coat micromorphologies of Rhodiola, which includes more
than 70 species. Recently, many molecular systematic studies have been conducted, and
Rhodiola has been an ideal material on which conduct research on radiated taxa [
15
,
16
,
25
,
29
],
but few studies have integrated the ornamentation of seed coats.
In this research, we integrated morphological studies, SEM and ITS using PCA and a
phylogenetic analysis for the delimitation of Rhodiola. A morphological comparison indi-
cated that the Lhünzêpopulation is similar to that of R. stapfii. In contrast, a phylogenetic
analysis showed that the Lhünzêpopulation is more closely related to R. smithii and R.
humilis than R. stapfii phylogenetically. However, scale-like leaves were identified in the
rhizome apex of the Lhünzêpopulation, whereas the leaves in the rhizome apex of R. smithii
and R. humilis were developed. The Namling populations are morphologically similar to
those of R. prainii, but the PCA results show that they can be easily differentiated by the
leaf shape (the length of the leaf, width of the leaf, length of between the widest part of
blade and base of petiole and length of the petiole). A phylogenetic analysis shows that the
Namling populations form a monophyletic clade with the species of Sect. Trifida and Sect.
Prainia. In this monophyletic clade, the Namling populations were placed at the base.
Thus, based on the phylogenetic analysis, leaf morphological analysis and habitat in-
formation, we believe that the Lhünzêpopulation and Namling population are distinct new
species of Rhodiola that have not yet been described, and will provide detailed information
to help understand the radiation of Rhodiola.
5. Description of the New Species
1. Rhodiola wangii S.Y. Meng sp. nov. (Figures 4and 5)
urn:lsid:ipni.org:names: 77260717-1.
Type:
—China. Xizang, LhünzêCo., 28
◦
06
0
00
00
N, 91
◦
55
0
53
00
E, 4914 m, 20 July 2014, S.Y.
Meng et al. MHW0071 (holotype PEY0067593, isotype, PEY0068681).
Diagnosis:—Similar to Rhodiola stapfii (Raymond-Hamet) S.H. Fu but differs in having an
intensely broad rhombus and alternate leaves, a distinct petiole, stamens that are gathered
together and have reflexed purple scales. (vs. middle stem leaves 5- or 6-verticillate, ovate
to ovate-oblong, white nectar scales).
Description:
—A low and delicate herbaceous perennial, 0.5–1 cm high. Caudex nearly
erect, fewer branches, slightly thicker, usually 4–8 mm across; apical part often short,
branched and accrescent, crowned by the scaly radical leaves. Scaly radical leaves membra-
nous, persistent, purple, long ovate with an entire margin, 1.4–1.7 mm long,
0.8 mm
wide.
Roots very slender. Flowering stems 1–3 from the apex of each caudex branch, deciduous,
0.5–1 cm long, erect, simple, terete, smooth. Leaves alternate, flattened, broad rhombus,
closely arranged on the stem, ascending-spreading, distinct petiole, spurless, glabrous,
5–7 mm long, 2–5 mm wide, entire. Inflorescences terminal, 1–3 flower buds form cymes,
inconspicuous bracteates, bracts leafy. Flower green, 4(5)-merous, dioecious. Female flow-
ers (
♀
) white-green, sepal 4 (5), free, long triangular, apex acuminate, entire, green, slightly
fleshy, 1.2–1.6 mm long, 0.7–0.8 mm wide. Petals 4 (5), triangular free, green, with a short
tip at the apex, 2 mm long, 0.8 mm wide, entire along the margin. Nectar-scales purple,
trapezoid, rolling outward, truncate at the apex, 0.5 mm long, 0.4 mm wide. Carpel 4–5,
free, erect, triangular ovate, ca. 2 mm long, style 0.5 mm long, curved outward. Follicles
erect. Ovules ca. 5–9 in each locule. Seed orbicular-ovate ca. 0.8 mm long, 0.6 mm wide.
Male flowers (
♂
) 4(5)-merous, sepals 4(5), green, free, long triangular, with a short tip at
the apex, 1.2–1.5 mm long, 0.8–1.0 mm wide. Petals 4 (5) free, pale green, 1.8–2.0 mm long,
0.8–1.0 mm wide. Stamens 8–10, shorter than petals, antepetalous ones inserted 0.5 mm
from petal base, long ca. 1.8 mm, antesepalous ones ca. 2 mm long, anther yellow. Nectar
scales 4(5), broadly quadrangular, purple-red, 0.5 mm long, 0.2 mm wide. Carpel 4(5),
erect, undeveloped.

Diversity 2022,14, 289 8 of 13
Distribution and Habitat:
—Perennial herb on mountain slopes, 4914 m. The distribution
of R. wangii S.Y. Meng is somewhat limited (Figure 6). To date, only one population has
been found on an arid hillside in the southeast region of Xizang, China.
Phenology:—Flowers from July to August, and fruits from August to September.
Etymology:
—The epithet ‘wangii’ is used to commemorate the famous Chinese botanist
and plant science popularization pioneer, Professor Wang Jinwu, Peking University. He
published many popular articles and an illustrated handbook of botanical taxonomy, which
promoted public attention and love for plants.
Common name (assigned here):—Jing Wu Hong Jing Tian (劲武红景天; Chinese name).
Proposed IUCN conservation status:
—The new species grows in the arid meadows of Mt.
Shangala. We collected only one population near Mt. Shangala, while another population
was found between the road of LhünzêCounty to Comai County in LhünzêCounty in 2021.
Although the habitat of the Qinghai–Tibet Plateau is relatively stable, more active economic
and construction activities, such as grazing, may affect the population. The species is
considered to be “Vulnerable” (VUD1) according to the IUCN Red List Criteria [30].
Figure 4.
Rhodiola wangii S.Y. Meng. (
A
). Rhizome and flowering stem; (
B
). Female flower; (
C
). Nectar;
(
D
). Male flower; (
E
). Petal and Stamens; (
F
). Sepal; (
G
). Follicles; (
H
). Seeds. Drawing by Ye Lv
from PEY0067593.

Diversity 2022,14, 289 9 of 13
Diversity 2022, 13, x FOR PEER REVIEW 10 of 14
Figure 5. Rhodiola wangii S.Y. Meng. (A). Rhizome and flowering stem; (B). Female plants; (C). Male
plants.
Figure 6. Geographic distribution. Blue dot shows Rhodiola wangii S.Y. Meng. Red dots show R.
namlingensis S.Y. Meng.
2. Rhodiola namlingensis S.Y. Meng sp. nov. (Figures 7 and 8)
urn:lsid:ipni.org:names: 77260718-1.
Type:—China. Xizang: Namling Co., 30°04′91″ N, 89°06′27″ E, 4208 m, 18 September 2015,
S.Y. Meng et al. 2015091802 (holotype, PEY0067596; isotype PEY0067595).
Diagnosis:—Similar to Rhodiola prainii (Hamet) H. Ohba but differs in its exerted alternate
leaves, more than four stem leaves, thick leaf blades, obovate to inverted triangle, short
petiole (vs. stem leaves 4, verticillate, oblong-elliptic leaf blades, ovate, broadly ovate, or
reniform-orbicular, base abruptly narrowed to long attenuate.)
Description:—A perennial herb, 2–4 cm tall. Roots slightly thicker, branches, 4–9 cm long.
Caudex cylindrical, slender, 2–7 mm thick, erect, the apical part densely covered with
Figure 5.
Rhodiola wangii S.Y. Meng. (
A
). Rhizome and flowering stem; (
B
). Female plants; (
C
). Male plants.
Diversity 2022, 13, x FOR PEER REVIEW 10 of 14
Figure 5. Rhodiola wangii S.Y. Meng. (A). Rhizome and flowering stem; (B). Female plants; (C). Male
plants.
Figure 6. Geographic distribution. Blue dot shows Rhodiola wangii S.Y. Meng. Red dots show R.
namlingensis S.Y. Meng.
2. Rhodiola namlingensis S.Y. Meng sp. nov. (Figures 7 and 8)
urn:lsid:ipni.org:names: 77260718-1.
Type:—China. Xizang: Namling Co., 30°04′91″ N, 89°06′27″ E, 4208 m, 18 September 2015,
S.Y. Meng et al. 2015091802 (holotype, PEY0067596; isotype PEY0067595).
Diagnosis:—Similar to Rhodiola prainii (Hamet) H. Ohba but differs in its exerted alternate
leaves, more than four stem leaves, thick leaf blades, obovate to inverted triangle, short
petiole (vs. stem leaves 4, verticillate, oblong-elliptic leaf blades, ovate, broadly ovate, or
reniform-orbicular, base abruptly narrowed to long attenuate.)
Description:—A perennial herb, 2–4 cm tall. Roots slightly thicker, branches, 4–9 cm long.
Caudex cylindrical, slender, 2–7 mm thick, erect, the apical part densely covered with
Figure 6.
Geographic distribution. Blue dot shows Rhodiola wangii S.Y. Meng. Red dots show R.
namlingensis S.Y. Meng.

Diversity 2022,14, 289 10 of 13
2. Rhodiola namlingensis S.Y. Meng sp. nov. (Figures 7and 8)
urn:lsid:ipni.org:names: 77260718-1.
Type:
—China. Xizang: Namling Co., 30
◦
04
0
91
00
N, 89
◦
06
0
27
00
E, 4208 m, 18 September 2015,
S.Y. Meng et al. 2015091802 (holotype, PEY0067596; isotype PEY0067595).
Diagnosis:
—Similar to Rhodiola prainii (Hamet) H. Ohba but differs in its exerted alternate
leaves, more than four stem leaves, thick leaf blades, obovate to inverted triangle, short
petiole (vs. stem leaves 4, verticillate, oblong-elliptic leaf blades, ovate, broadly ovate, or
reniform-orbicular, base abruptly narrowed to long attenuate.)
Description:
—A perennial herb, 2–4 cm tall. Roots slightly thicker, branches, 4–9 cm long.
Caudex cylindrical, slender, 2–7 mm thick, erect, the apical part densely covered with
scaly radical-leaves. Scaly radical-leaves broadly triangular with entire margin, persistent,
acuminate at the apex, 1.5–1.8 mm long, 1.5 mm wide, reddish brown. Flowering stems 1–4
from each branch apex of rhizomes, erect, simple, terete, glabrous. Leaves alternate, densely
arranged on the upper part, ascending-spreading, spurless, thick herbaceous, flattish,
yellowish green, obovate to inverted triangle, round at the apex; very short attenuate at the
base; entire along the margin, 12–16 mm long, 6–8 mm wide, glabrous on both surfaces. The
costa not obvious, with a short petiole. Inflorescences simple or few branches, corymbiform,
1–4 flowered; bracts shortly petiolate, obovate, 5–7
×
3–4 mm. Flowers bisexual, white
or red, unequally 5-merous; pedicel 4–6 mm. Sepals 5, green, succulent, triangular-ovate,
5–7 mm long, 3–3.5mm wide, obtuse at the apex, entire. Petals 5, white or red, sometimes
white with red plaques, oblong-ovate, 10–12 mm long, the united part 0.5 mm long, the
free part 9–11 mm long, 6–8 mm wide, apex acuminate, tapering to the base. The petals do
not fully open at maturity but stand upright surrounded by stamens and ovaries. Stamens
10, slightly shorter than petals, antepetalous ones inserted 2–3 mm from petal base, long
ca. 5 mm, antesepalous ones 7–8 mm long, the filaments slender, sub-linear, anther tip,
blue. Nectar scales trapezoid, ca. 1 mm long, ca. 0.8 mm wide, apex emarginate. Carpels 5,
slightly connate at base, erect, long elliptic, 6–7 mm long, style 2–3 mm long, erect; each
carpel has about 20 ovules. Seeds long elliptic, 1.5 mm long and 0.5 mm wide.
Distribution and Habitat:
R. namlingensis was only known from southeast Xizang (Nam-
ling), China (Figure 6). Now, two populations have been found. It grows in gravel crevices
or rock crevices on the beach of the Jiacuo Zangbo Valley, between 3800 and 4000 m above
sea level.
Etymology:—The specific epithet is derived from Namling county, southeast of Xizang, China.
Phenology:—Flowering in August to September, fruiting in September to October.
Common name (assigned here):
—Nan Mu Lin Hong Jing Tian (
南木林红景天
; Chinese name).
Proposed IUCN conservation status:
—This new species is only known from southeast
Xizang (Namling) where two populations were found in gravel crevices or rock crevices on
the beach of the Jiacuo Zangbo Valley, between 3800 and 4000 m above sea level. The species
is considered to be “Vulnerable” (VUD1) according to the IUCN Red List Criteria [30].
Additional specimens examined (paratype):
—China. Xizang: Namling Co., 4313 m,
18 September 2015
, S.Y. Meng et al. 2015091804 (PEY0068680, PEY0067594); Namling
Co., 4313 m, 30 July 2015, S.Y. Meng & Z.M. Wang MWH110 (PEY0066822); Namling Co.,
4212 m, 11 August 2010, S.Y. Meng msy05 (PEY0068679).

Diversity 2022,14, 289 11 of 13
Diversity 2022, 13, x FOR PEER REVIEW 12 of 14
Figure 7. Rhodiola namlingensis S.Y. Meng. (A). Rhizome and flowering stem; (B). Petal and stamens;
(C). Sepal; (D). Carpel; (E). Nectar; (F). Follicle; (G). Seed. Drawing by Ye Lv from PEY0067595.
Figure 8. Rhodiola namlingensis S.Y. Meng. (A). A plant and its habitat; (B). Side face of the plant.
Supplementary Materials: The following supporting information can be downloaded at:
www.mdpi.com/xxx/s1, Figure S1: Leaf measurement. Figure S2: ML tree based on ITS sequences
for these two new Rhodiola species and their close relatives. Table S1: Plant materials of 36 accessions
of the Rhodiola taxa and two outgroup taxa with their collection locality, voucher information, and
accession numbers of ITS sequences reported by Zhang et al. (2014).
Author Contributions: The experimental design was completed by S.-Y.M. and Z.-M.W. Sample
collection and treatment were conducted by S.-Y.M. The data were analyzed, and the figures and
Figure 7.
Rhodiola namlingensis S.Y. Meng. (
A
). Rhizome and flowering stem; (
B
). Petal and stamens;
(C). Sepal; (D). Carpel; (E). Nectar; (F). Follicle; (G). Seed. Drawing by Ye Lv from PEY0067595.
Diversity 2022, 13, x FOR PEER REVIEW 12 of 14
Figure 7. Rhodiola namlingensis S.Y. Meng. (A). Rhizome and flowering stem; (B). Petal and stamens;
(C). Sepal; (D). Carpel; (E). Nectar; (F). Follicle; (G). Seed. Drawing by Ye Lv from PEY0067595.
Figure 8. Rhodiola namlingensis S.Y. Meng. (A). A plant and its habitat; (B). Side face of the plant.
Supplementary Materials: The following supporting information can be downloaded at:
www.mdpi.com/xxx/s1, Figure S1: Leaf measurement. Figure S2: ML tree based on ITS sequences
for these two new Rhodiola species and their close relatives. Table S1: Plant materials of 36 accessions
of the Rhodiola taxa and two outgroup taxa with their collection locality, voucher information, and
accession numbers of ITS sequences reported by Zhang et al. (2014).
Author Contributions: The experimental design was completed by S.-Y.M. and Z.-M.W. Sample
collection and treatment were conducted by S.-Y.M. The data were analyzed, and the figures and
Figure 8. Rhodiola namlingensis S.Y. Meng. (A). A plant and its habitat; (B). Side face of the plant.
Supplementary Materials:
The following supporting information can be downloaded at: https:
//www.mdpi.com/article/10.3390/d14040289/s1, Figure S1: Leaf measurement. Figure S2: ML tree
based on ITS sequences for these two new Rhodiola species and their close relatives. Table S1: Plant
materials of 36 accessions of the Rhodiola taxa and two outgroup taxa with their collection locality,
voucher information, and accession numbers of ITS sequences reported by Zhang et al. (2014).

Diversity 2022,14, 289 12 of 13
Author Contributions:
The experimental design was completed by S.M. and Z.W. Sample collection
and treatment were conducted by S.M. The data were analyzed, and the figures and tables prepared
with assistance from L.Y. and Z.W. The manuscript was drafted by S.M. edited the manuscript for
structure, language, and scientific content. All authors have read and agreed to the published version
of the manuscript.
Funding:
This research was funded by the National Natural Science Foundation of China (
No. 31600159
).
Institutional Review Board Statement: Not applicable.
Data Availability Statement: Not applicable.
Acknowledgments:
The authors thank the Core Facilities at the School of Life Sciences, Peking
University for assistance with scanning electron microscope observation. We also thank Hong-ya Gu,
Guang-yuan Rao and Sodmergen, Jia-chen Hao, and Yi-hao Shi for field assistance.
Conflicts of Interest: The authors declare no conflict of interest.
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