Research Article |
Corresponding author: Soo-Rang Lee ( ra1130@chosun.ac.kr ) Academic editor: Yasen Mutafchiev
© 2022 Tae-Young Choi, Dong Chan Son, Takashi Shiga, Soo-Rang Lee.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Choi T-Y, Son DC, Shiga T, Lee S-R (2022) Phedimus daeamensis (Crassulaceae), a new species from Mt. Daeam in Korea. PhytoKeys 212: 57-71. https://doi.org/10.3897/phytokeys.212.82604
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Phedimus individuals from Mt. Daeam, once referred to as Phedimus sikokianus, exhibit certain morphological characters that are unique within the genus. Phedimus is one of the most notorious groups for taxonomic problems due to the high morphological variation found in leaf shape, stem numbers, phyllotaxis and seed structure. Taxa in Phedimus also easily hybridize, further leading to taxonomic confusion. To carefully confirm the identity of the putative new species from Mt. Daeam, we examined morphological characters from ~100 herbarium sheets of six closely related Phedimus species. A molecular phylogenetic approach was also employed to delimit the species boundary and infer the phylogenetic relationships among the seven Phedimus species, including the species from Mt. Daeam. Both morphological and molecular phylogenetic results indicated that the species found on Mt. Daeam is a new species that is more closely related to P. middendorffianus and P. takesimensis than to the remaining four Phedimus species. Here, we provided a full description of the new species P. daeamensis as well as an updated key for the seven Phedimus species examined.
Molecular diagnosis, new species, Phedimus, phylogeny
Until
There are eight Phedimus species including two endemic species and one with two infraspecific taxa in Korea [Phedimus aizoon var. aizoon, P. aizoon var. latifolius (Maxim.) H. Ohba, P. kamtschaticus (Fisch. & C.A. Mey.) ‘t Hart, P. latiovalifolius (Y.N. Lee) D.C. Son & H.J. Kim, P. middendorffianus (Maxim.) ‘t Hart, P. selskianus (Regel & Maack) ‘t Hart, P. takesimensis (Nakai) ‘t Hart, P. zokuriensis (Nakai) ‘t Hart] (
Mt. Daeam, is a high-altitude mountain (> 1300 m) in Korea, which owing to its diverse geographical and environmental characteristics is an area of substantial biodiversity (
In the present study, we report a new plant species, P. daeamensis T.Y. Choi & D.C. Son of the genus Phedimus subgenus Aizoon. We described the morphological characters and habitat features of the new species with a detailed botanical illustration in gray-scale hand drawing. To delimit the species boundary from the six closest related taxa, we performed morphological observations as well as a molecular phylogenetic study. A key to the Korean species of Phedimus (subgenus Aizoon) including the new species was established based on the examined morphological characters.
We collected four living samples of P. daeamensis and prepared a voucher specimen. Referring to the relevant protologues, floras, and monographs (
Summary of diagnostic characters observed in Phedimus daeamensis and the two morphologically closest taxa. The full diagnostic morphological characters of all seven Phedimus taxa investigated in the study are presented as supplementary information (Suppl. material
P. middendorffianus | P. sikokianus | P. daeamensis | |
---|---|---|---|
Leaves | alternate | opposite | alternate |
blade shape | linear-spatulate | widely oblanceolate to obovate | obovate |
blade size | 1.2–4 cm long, 0.2–0.5 cm wide | 0.8–2.3 cm long, 0.6–1.3 cm wide | 1–2.3 cm long, 0.5–1.2 cm wide |
margins | margin apically serrate 2–3, apex obtuse | margin apically to mid crenate 2–4, apex rounded | margin apically to mid serrate 4–5, apex obtuse |
Calyx lobes | 5, linear, 2–3 mm long, apex obtuse | 5, lanceolate, 2–3 mm long, apex obtuse | 5, lanceolate, 3–4 mm long, apex obtuse |
Seeds | obovoid | ellipsoid, ca. 0.8–1 mm long | obovoid, ca. 0.7–1 mm long |
To delimit the new species from the six most closely related taxa we examined their phylogeny. Sixteen samples of the seven taxa (three P. daeamensis and remaining of the six closely relatives) were collected from 14 localities across South Korea and Japan (see Suppl. material
We also included seven accessions of three Phedimus taxa (P. latiovalifolius, P. aizoon var. floribundus, P. takesimensis) downloaded from GenBank to test the species boundaries across all Phedimus taxa co-occurring in Korea and Japan (Suppl. material
We used the plant habit, leaf shapes, and margins to distinguish the newly described Phedimus species (
Republic of Korea. Gangwon-do, Inje-gun, Buk-myeon, Wolhak-ri, Mt. Daeam. Elevation 1,000 m. 20 August 2014. K.H. Lee & S.K. So 0001 (holotype
Rhizome woody, elongated. Roots not tuberous; rootstock not robust. Stems numerous, more basally branched, tufted, creeping, ascending, 12–21 cm long, glabrous. Leaves alternate, sessile, coarsely arranged; leaf blade obovate, 1–2.3 cm long, 0.5–1.2 cm wide, flat, base narrowly cuneate, margin apically to mid serrate 4–5×, entire at base, apex obtuse; lower leaves almost all entire. Inflorescence corymbiform-cymose, many-flowered; bracts leaf-like. Flowers bisexual, mostly 5-merous, shortly pedicelled. Calyx tube 2.1–3.2 mm long; lobes spurless, lanceolate, 1–1.2 mm long, apex obtuse. Petals free, yellow, lanceolate to oblong, 5–6.5 mm long, abaxially keeled, apex acuminate, spreading at anthesis. Stamens 10, in 2 series, erect, shorter than petals, those opposite to petals adnate to them to 1/4 of length from the base; anthers red, ellipsoid, ca. 1 mm long; filaments yellow. Pistils 4.5–5 mm long; ovaries ca. 2.5 mm long, connate at the base; styles slender, 2–3 mm long. Carpels 5, erect, equaling or slightly shorter than the petals, adaxially gibbous, shortly connate at the base. Follicles greenish, stellately and horizontally spreading, ca. 4 mm long, with a very short beak. Seeds 0.8–0.9 mm long, brown, obovoid, scalariform, ribbed, striate.
Flowers in May to June, fruiting in July to August.
Republic of Korea (Prov. Gangwon). Stony cliffs and rock crevices, at ca. 1000 m.
The specific epithet, “daeamensis”, is based on the name of the location, Mt. Daeam, where Phedimus daeamensis was discovered.
Dae-am-gi-rin-cho.
In total, 32 sequences of two DNA regions (ITS and psbA-trnH IGS) were newly obtained from the 16 accessions of P. daeamensis and the six most closely related taxa (Suppl. material
Results of the cpDNA data sets used in this study. The out-group taxa were included in the analyses, except for the K2P distance.
ITS | psbA-trnH IGS | |
---|---|---|
Sequence length (bp) | 572–579 | 234–266 |
Aligned length (bp) | 588 | 272 |
Mean G+C ratio (%) | 50.5 | 22.5 |
No. of variable characters | 144 | 29 |
No. of parsimony informative characters (%) | 120 (85.7) | 24 (82.8) |
K2P distance (mean)* | 0–0.043 (0.023) | 0–0.048 (0.018) |
Overall, the inferred phylogenies from the two regions differ, particularly in the basal nodes (Figs
1 | Stems 1–3, erect; leaves lanceolate, apex acuminate | Phedimus aizoon |
– | Stems many, ascending to prostrate; leaves spathulate, obovate, oblanceolate or elliptic-oblanceolate, apex obtuse to rounded | 2 |
2 | Roots thick, robust; stems 20–50 cm long, ascending | 3 |
– | Roots fibrous; stems less than 20 cm long, prostrate | 4 |
3 | Leaves oblanceolate or spathulate, margins serrate in upper half | Phedimus takesimensis |
– | Leaves spathulate, obovate or elliptic, margins entire or with few acute to obtuse teeth | Phedimus kamtschaticus |
4 | Leaves broadly ovate, margins irregularly dentate | Phedimus latiovalifolius |
– | Leaves obovate to linear, margins serrate or crenate | 5 |
5 | Leaves obovate, somewhat concave | 6 |
– | Leaves linear-spathulate or elliptic-oblanceolate, flat | 7 |
6 | Leaves opposite, margins crenate, seeds ellipsoid | Phedimus sikokianus |
– | Leaves alternate, margins serrate, seeds obovoid | Phedimus daeamensis |
7 | Stems prostrate; leaves 1.2–2.5 cm × 3–5 mm, with 2 or 3 teeth | Phedimus middendorffianus |
– | Stems decumbent; leaves 2.5–3.5 cm × 1.1–1.6 cm, with many teeth | Phedimus zokuriensis |
Phedimus has been a rather unexplored taxonomic group until the resurrection of the genus by
Overall, our study characterized the morphological distinctiveness of the newly described species (P. daeamensis) from the six closest related congeners. However, most characters of examination were vegetative and thus showed significant infraspecific variation across varying environments. Phedimus kamtschaticus and P. aizoon showed substantial morphological variation. Although P. kamtschaticus, the most commonly occurring Phedimus species in Korea (
Notably, phylogenetic trees reconstructed based on the ITS and psbA-trnH IGS regions were consistent with the morphological results. In both ML trees from nrITS and cpDNA, the three morphotypes sharing the same morphological characters as the newly reported P. daeamensis came out as a monophyletic group or as an unresolved polytomy. Phedimus daeamensis was always placed separate from both P. kamtschaticus and P. sikokianus, but the phylogenetic relationship of the species with its closest related taxa was inconclusive because of low clade support and inconsistency between nrITS and cpDNA trees. In the ITS trees, P. daeamensis fell into the same clade as P. takesimensis and P. middendorffianus (Fig.
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT) (No. NRF-2021R1A6A3A01086610). We thank Dr. Jungsim Lee and Kang Hyup Lee for providing valuable specimens and materials. We also thank Kyungsoo Eo for providing Fig.
Tables S1–S6
Data type: occurence, morphology (docx./xslx. files in zip. archive)
Explanation note: Table S1. List of examined specimens for morphological study. Table S2. Diagnostic characters observed in Phedimus daeamensis and the six closest related taxa. Table S3. Voucher information and GenBank accession numbers for the 16 accessions of P. daeamensis and closely related taxa examined in this study. Table S4. PCR/sequencing primers and PCR cycling conditions for the DNA regions examined in this study. Table S5. Voucher information and GenBank accession numbers for 10 Phedimus accessions downloaded from GenBank. Table S6. Variable sites obtained from the ITS and psbA-trnH IGS regions.
Figure S1
Data type: Image (Adobe PDF file)
Explanation note: Figure S1. Bayesian inference tree for individuals of P. daeamensis and related taxa based on ITS. Numbers above branches are posterior probabilities.
Figure S2
Data type: Image (Adobe PDF file)
Explanation note: Figure S2. Bayesian inference tree for individuals of P. daeamensis and related taxa based on psbA-trnH IGS. Numbers above branches are posterior probabilities.