Saussurea bogedaensis Yu J.Wang & J.Chen, PloS ONE 13(7): e0199416 (12) (2018)

Baasanmunkh, Shukherdorj, Nyamgerel, Nudkhuu, Bayarmaa, Gun-Aajav, Oyuntsetseg, Batlai, Oyundelger, Khurelpurev & Choi, Hyeok Jae, 2020, A new record of critically endangered Saussurea bogedaensis (Asteraceae) from Dzungarian Gobi, Mongolia, PhytoKeys 160, pp. 109-121 : 109

Saussurea bogedaensis Yu J.Wang & J.Chen, PloS ONE 13(7): e0199416 (12) (2018) Figs 1 , 3

Morphological identification.

Saussurea bogedaensis (Fig. 1 ) was recently discovered on Bogeda Mt in Xinjiang, China by Chen and Wang (2018) (Fig. 3 ). This species is very similar to S. involucrata and S. orgaadayi (Fig. 2 ), but several morphological characteristics of the bracts, involucres and phyllaries differentiate them ( Chen and Wang 2018). In particular, S. bogedaensis differs by having elliptic, apically obtuse stem leaves (Fig. 1C ) vs. lanceolate, long-acuminate stem leaves in S. orgaadayi (Fig. 2A ); dirty white pappus colour (Fig. 1D ) vs. straw-coloured pappi in S. orgaadayi (Fig. 2D ); densely pubescent phyllaries (Fig. 1E ) vs. glabrous phyllaries in S. involucrata ; and campanulate involucres in S. bogedaensis vs. hemispherical involucres in S. involucrata .

Genetic identification.

The combined sequence dataset consisted of 15 samples, including the outgroup, Jurinea multiflora . The sequence dataset comprised 2,315 characteristics, of which 20 were parsimony-informative, 108 were variable and 2,169 were constant. The gene boundaries on the ITS - trnK - trnH-psbA - rbcL multi-locus alignment were as follows: ITS: 1-656, trnK: 657-1,284, trnH-psbA: 1,285-1,680 and rbcL: 1,681-2,315. The final ML optimisation likelihood of ML analysis was: Inl = -3650.7353. A single most parsimonious tree was generated by MP analysis with a tree length of 105 steps, consistency index: 1.0, retention index: 1.0 and composite index: 1.0. The BI phylogeny, including BI posterior probability values, as well as ML and MP bootstrap support values, are provided in Fig. 4 .

Our genetic identification revealed a similar topology to that of Chen and Wang (2018) and confirms each distinct clade of S. bogedaensis , S. involucrata and S. orgaadayi , respectively (Fig. 4 ). Three individuals of newly-revealed Saussurea specimens from Baitag Bogd Mt formed one cluster with the Chinese S. bogedaensis with high support: BI/ML/MP = 1/100/99. Additionally, sequence divergence amongst the three species was 0-0.002% in our S. bogedaensis specimens, whereas there was 3.02% sequence divergence in S. involucrata and 2.04% sequence divergence in S. orgaadayi . Sequence alignment revealed that the Mongolian and Chinese S. bogedaensis share several specific nucleotide residues that are different from those of other Saussurea species (Fig. 5 ). The other three samples (Fig. 2 ) from Munkhkhairkhan Mt in the MA region clustered with S. orgaadayi from China (BI/ML/MP = 1/100/99). Therefore, our study proves that the Saussurea samples from the DzG and MA regions are S. bogedaensis (Fig. 1 ) and S. orgaadayi (Fig. 2 ), respectively. Our genetic results provide only the genetic differences between the three related species in the subg. Amphilaena and not a true phylogeny of all related Saussurea species.

General distribution and habitat.

Mongolia (Dzungarian Gobi, Baitag Bogd Mt) and China (Xinjiang, Bogeda Mt). In Mongolia, S. bogedaensis grows on high mountain rocky slopes, screes, boulders and river banks in the alpine belt at altitudes of 2400-3300 m a.s.l. This species is closely related to S. involucrata and S. orgaadayi . However, the three species are geographically isolated: S. bogedaensis occurs in the Dzungarian basin and the eastern Chinese Tien-Shan Mts and S. involucrata occurs in the Tien-Shan Mts (which cover parts of China and Central Asian states), whereas S. orgaadayi is present in the Altai Mts (which cover parts of China, Mongolia and Russia) (Fig. 3 ), according to Raab-Straube (2017) and Chen and Wang (2018).

Conservation status.

Saussurea bogedaensis is new to the Mongolian flora and occurs in the Baitag Bogd Mt in the DzG region. Individuals of the species were found in a few locations, namely in Baitag Bogd Mt and Altan Ovoo in the DzG region (Fig. 3 ). During our field surveys, we detected two different populations, which in total, accounted for fewer than 600 individuals in this region. This species is under threat, particularly owing to human interference and random cutting. Thus, S. bogedaensis has been assessed as Critically Endangered [CR C2a(i)] in Mongolia according to the IUCN Red List categories and criteria ( IUCN 2019). This species was also evaluated as critically endangered in China ( Chen and Wang 2018). In situ studies on the reproductive biology of S. bogedaensis are needed to more accurately assess the conservation status of this species in Mongolia.

Specimens examined (new record).

Mongolia. Dzungarian Gobi region: Khovd Province, Uyench sum, Baitag Bogd Mt, Buduun Khargait river, 45°13'14.52"N, 90°55'12.97"E, 2742 m a.s.l., 28 Jul 2019, Sh. Baasanmunkh et al., 20190698, 20190699, 20190700 (UBU). The samples from this site were used for the molecular analysis confirming the identity of the Mongolian plants as S. bogedaensis .

Figures

Figure 1. Saussurea bogedaensis in Buduun Khargait river, Baitag Bogd Mt, Uyench sum, Khovd Province, Mongolia. A general habit in Baitag Bogd Mt, DzG region B fruiting C leaves D pappus E phyllaries. Photos: 28 July 2019, Sh. Baasanmunkh.

Figure 2. Saussurea orgaadayi in Khukh Nuur, Munkhkhairkhan sum, Khovd Province, Mongolia A general habit in Munkhkhairkhan Mt, MA region B fruiting C flowering D pappus E phyllaries. Photos: 29 July 2016, B. Oyuntsetseg (A, C) Sh. Baasanmunkh (B, D, E).

Figure 3. Distribution of S. bogedaensis (red dots), S. involucrata (blue dots) and S. orgaadayi (green dots) in Mongolia, Russia and Chinese Tien-Shan Mts based on field surveys and herbarium materials as well as specimens from China based on the publications of Chen and Wang (2018) and Chen et al. (2019). Region numbers on the Mongolian map are phytogeographical regions according to Grubov (1982): 6 - Khovd, 7 - Mongolian Altai, 10 - Depression of Great Lakes and 14 - Dzungarian Gobi.

Figure 4. Phylogenetic tree based on concatenated sequence alignments of nrDNA (ITS) and cpDNA (trnK, trnH-psbA, and rbcL) regions. Bayesian Inference (BI) posterior probability support values above 90 % (bold), Maximum Likelihood (ML) and Maximum Parsimony (MP) bootstrap support values above 70 % are shown in the branches in the following order BI / ML / MP. The new samples of S. bogedaensis and S. orgaadayi originated from Mongolia are in red and black bolds, respectively.

Figure 5. Multiple sequence alignment of combined nr DNA (ITS) and cpDNA (trnK, trnH-psbA and rbcL) sequences. ITS region shows more differences than cpDNA regions amongst those closely related species. (*) - no differences found between species.