Chrysosplenium is a genus of small perennial herbaceous plants widely distributed in the Northern Hemisphere, holding a prominent taxonomic position within Saxifragaceae phylogeny^[1-3]. Chrysosplenium is readily distinguished from other related genera, such as Bergenia, Saxifraga, and Tiarella, by its tetramerous flowers and petaloid sepals^[4]. Chrysosplenium species contain highly hydroxylated, methoxylated flavonoids and triterpenoids with significant medicinal value, with some species also used ornamentally^{[5, 6]}. To date, more than 80 species of Chrysosplenium have been documented, including 40 species in China^{[7, 8]}, 24 (60%) of which are endemic to China, primarily found in the Shaanxi, Sichuan, and Yunnan provinces^[9-11].

During a field investigation in Yanji, northeast China, we collected a distinctive species of Chrysosplenium. While morphologically similar to C. pilosum Maxim., the specimens were distinguished by the presence of four large, accumulated leaves at the top of sterile branches. Extensive literature review, specimen examination, and material observations^[8-16] confirmed that the Yanji specimens belong to C. fallax Koldaeva, a species recently published by Russian scholars in 2021^[10]. C. fallax has a previously reported distribution restricted to the Russian Far East, including the Shkotovsky District, Ussuriysky and Vladivostoksky (except islands) UrbanOkrugs. Therefore, our identification of C. fallax as a newly recorded species in Yanji, China, is significant. In this study, we provide a detailed morphological description of C. fallax, along with accompanying color photographs. Furthermore, we performed a phylogenetic analysis of C. fallax based on 78 chloroplast coding sequences. Voucher specimens were deposited in the Herbarium of South-Central Minzu University (HSN).

1.   Materials and Methods

1.1   Morphological observations

The morphological characteristics of plant material from field and herbarium specimens were studied using a dissecting microscope (SMZ171, Motic, China). A scanning electron microscope(SEM) was employed to observe seed morphology. Seed materials were collected from the field and dried with silica gel. Pre-treatment of seeds followed previous research^[12]. A Hitachi SU8010 SEM was used for observations and photography. Seed size and surface were determined using at least 15 seeds.

1.2   Phylogenetic analysis

To confirm the placement of C. fallax within Chrysosplenium, phylogenetic analysis was conducted using chloroplast protein-coding genes. Analysis included 45 species of Chrysosplenium as the in-group and Peltoboykinia tellimoides (Maxim.) H. Hara as the out-group. The chloroplast genome of C. fallax was newly generated in this study, while the sequences of the other species were obtained from GenBank (https://www.ncbi.nlm.nih.gov/). The GenBank accession numbers for all species are listed in Table 1.

Table  1.  Species names and GenBank accession numbers used in this study

Number	Taxon	Section	Chloroplast genome
1	Chrysosplenium album Maxim.	Oppositifolia	OK336556
2	Chrysosplenium alpinum Schur	Oppositifolia	OR397748
3	Chrysosplenium aureobracteatum Y. I. Kim & Y. D. Kim	Oppositifolia	MG878089
4	Chrysosplenium biondianum Engl.	Oppositifolia	OK336542
5	Chrysosplenium delavayi Franch.	Oppositifolia	OK336539
6	Chrysosplenium echinus Maxim.	Oppositifolia	OK336557
7	Chrysosplenium fallax Koldaeva	Oppositifolia	OR639854
8	Chrysosplenium fauriae Franch.	Oppositifolia	OK336561
9	Chrysosplenium grayanum Maxim.	Oppositifolia	OK336555
10	Chrysosplenium kamtschaticum Fisch. ex Seringe	Oppositifolia	MT371065
11	Chrysosplenium kiotense Ohwi.	Oppositifolia	OK336558
12	Chrysosplenium lectus-cochleae Kitagawa	Oppositifolia	OK336550
13	Chrysosplenium macrospermum Y. I. Kim & Y. D. Kim	Oppositifolia	OK336562
14	Chrysosplenium macrostemon Maxim. ex Franch. et Sav.	Oppositifolia	OK336560
15	Chrysosplenium nepalense D. Don	Oppositifolia	OK336535
16	Chrysosplenium oppositifolium L.	Oppositifolia	OR397749
17	Chrysosplenium pilosum Maxim.	Oppositifolia	OK336559
18	Chrysosplenium pilosum Maxim. var. valdepilosum	Oppositifolia	OR397753
19	Chrysosplenium qinlingense Z. P. Jien ex J. T. Pan	Oppositifolia	OK336549
20	Chrysosplenium ramosum Maxim.	Oppositifolia	MK973002
21	Chrysosplenium sinicum Maxim.	Oppositifolia	MK814606
22	Chrysosplenium valdivicum Hook.	Oppositifolia	OR397752
23	Chrysosplenium alternifolium L.	Alternifolia	OK336545
24	Chrysosplenium carnosum Hook. f. et Thoms.	Alternifolia	OK336564
25	Chrysosplenium davidianum Decne. ex Maxim.	Alternifolia	OK336537
26	Chrysosplenium flagelliferum Fr. Schmidt.	Alternifolia	OK336541
27	Chrysosplenium forrestii Diels	Alternifolia	OK336565
28	Chrysosplenium giraldianum Engl.	Alternifolia	OK336548
29	Chrysosplenium glossophyllum Hara	Alternifolia	OK336544
30	Chrysosplenium griffithii Hook. f. et Thoms.	Alternifolia	OK336547
31	Chrysosplenium griffithii var. intermedium (Hara) J. T. Pan	Alternifolia	OK336543
32	Chrysosplenium henryi Franch.	Alternifolia	OK336532
33	Chrysosplenium hydrocotylifolium Lévl. et Vant.	Alternifolia	OK336540
34	Chrysosplenium japonicum (Maxim.) Makino	Alternifolia	OK336554
35	Chrysosplenium lanuginosum Hook. f. et Thoms.	Alternifolia	OK336534
36	Chrysosplenium macrophyllum Oliv.	Alternifolia	MK973001
37	Chrysosplenium microspermum Franch.	Alternifolia	OK336546
38	Chrysosplenium nudicaule Bunge	Alternifolia	MZ424445
39	Chrysosplenium serreanum Hand.-Mazz.	Alternifolia	OK336538
40	Chrysosplenium taibaishanense J. T. Pan	Alternifolia	OK336552
41	Chrysosplenium tetrandrum (N. Lund) Th. Fries	Alternifolia	OR397750
42	Chrysosplenium uniflorum Maxim.	Alternifolia	OK336533
43	Chrysosplenium wrightii Franch. & Sav.	Alternifolia	OR397751
44	Chrysosplenium zhangjiajieense X. L. Yu, Hui Zhou & D. S. Zhou	Alternifolia	OK336563
45	Chrysosplenium zhouzhiense Hong Liu	Alternifolia	OK336551
46	Peltoboykinia tellimoides (Maxim.) Hara	—	MZ779205

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PhyloSuite v1.2.2^[17] was used to extract 78 protein-coding genes from the chloroplast genome. The coding sequences were aligned using MAFFT v7.4^[18], then combined using PhyloSuite v1.2.2^[17]. Maximum-likelihood (ML) analysis was performed using IQ-TREE v2.1.2^[19] with 1 000 bootstrap replicates. The best-fit substitution model (TVM+F+R4) was determined using ModelFinder^[20]. The Bayesian inference (BI) tree was obtained using MrBayes v3.2.6^[21], run for one million generations, one run, and two chains, with 25% of trees discarded as burn-in and trees sampled every 1 000 generations (1 000 trees sampled in total) using the GTR model. FigTree v1.4.3 (http://tree.bio.ed.ac.uk/software/fgtree/) was used for tree visualization.

2.   Taxonomic Treatment

宽卵叶金腰（新拟，Fig. 1）

Figure  1.  Morphology of Chrysosplenium fallax

A: Habitat; B: Vegetative plant; C: Fruiting plant; D: Structure of shoot system; E: Inflorescence; F: Capsules; G: Seed; H: Seed surface structure.

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Figure  2.  Phylogenetic tree of Chrysosplenium species based on ML and BI analyses using 78 chloroplast protein-coding genes

Values on nodes indicate ML bootstrap support values (left) and BI posterior probabilities (right).

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Chrysosplenium fallax Koldaeva, Phytotaxa 491(1): 039, Fig. 1-4, 2021.

Type: Russian Federation, Primorsky Krai, Vladivostoksky Urban Okrug, Muravyev-Amursky Peninsula, Malaya Pionerskaya River valley, edge of a coniferous-broad-leaf forest, moist habitat, 12 May 2017, M.N. Koldaeva 0115.

Perennial herbs, 10–20 cm high, hermaphroditic, pulpy, pubescent with long, white hairs, reddish when dry. Root fibrous and soft, 1.2–5 cm long, underground, plagiotropic, with 2–5 elongated internodes. Flowering stem single, erect, 14–20(–24) cm tall, light green to green, tetragonal in cross-section, middle part sparsely pubescent, base and apical part almost glabrous, with 2–7 sterile branches arising from all leaf axils. Vegetative shoots above-ground and underground. Underground stolons 1–4, 3 to 48 cm long, 1.5–2 mm in diameter, unbranched or weakly branched in distal part, white; Approximately 10-cm-long distal portion of stolon remains by end of growing season. Repent stolon-like shoots 3–8, evenly leafed; leaves 5–6 pairs, similar, small. Sterile branches orthotropic (axial and lateral), prostrate, repent, stolon-like, pubescent with long hairs, most densely aggregated at apical part; Axial sterile branches 6 to 21 cm long, with branches or non-branching; Lateral sterile branches 5 to 16 cm long, with basal internode elongated. Leaves simple, estipulate, petiolate. Basal leaves absent. Cauline leaves 2–6, opposite or rarely alternate, petioles 3–9 mm long, sparsely pilose; blade 3–13×4–19 mm, subflabellate or flabellate-rounded, apex subtruncate to rounded, base cuneate to broadly cuneate, adaxial surface glabrous, abaxial surface glabrous or with single hairs along veins at base, often with red specks, margins ciliate, with 5–7–9 smooth-serrated crenates. Leaves of sterile branches opposite, not evenly leafed, highly unequal, with largest ones acervate, resembling rosette at apex but not forming true rosette, apical part not rooted; leaves of axial sterile branches 4–9(–11) pairs; blade 2.1–5.6×2.0–3.7 cm (except uppermost one), distal 2–3 pairs largest, with short internodes (0.2–0.5 cm); blade rounded, rounded-ovate, or elliptical; base cuneate; margin undulate-crenate, crenate-sinuate, or almost smooth-ciliate, with 5–7 crenates on each side; leaves of lateral sterile branches (1–)2–4 pairs, acervate to resemble rosette at apex; pubescence of leaf abaxial side along main veins on 1^st or 2^nd pairs of lateral branches or 2^nd to 5^th pairs of axial branches; in upper pairs, pubescence becomes denser; blade adaxial side glabrous or with solitary hairs at periphery, sometimes with silvery dots; petioles sparsely pilose on both sides. Cymes compact, 5–18 flowered, surrounded by large, greenish-yellow bracts. Inflorescence branches and bracteal petioles with solitary long hairs. Bracteal leaves greenish-yellow, petioles 1–4 mm, pilose; blades 4–16×2–12 mm, flabelliform or broadly ovate to ovate, apex subtruncate to rounded, base cuneate to broadly cuneate, with 5–7–9 smoothed-serrated crenates, upper surface glabrous, densely silvery dotted, lower surface glabrous, greenish-gray. Flowers tetramerous, actinomorphic, goblet-shaped, yellow, sometimes with red specks, pedicels short (0.8–3 mm). Sepals 4, erect, convex outside, with tip slightly bent outward; external almost rounded 2.2×2.1 mm; internal ovoid 1.8×1.5 mm, shorter than external ones. Petals absent. Stamens 8, biseriate, ca. 2 mm long, equal to calyx, filaments filiform, 1.5 mm long. Anthers yellow, 2-locular, ca. 0.5 mm long, longitudinally dehiscent. Pistil 2-carpellate, subsuperior, ovary 1-locular, ovules at two parietal placentae, styles 2, erect, slightly divergent, ca. 1 mm long, stigma round, disc absent; nectary not prominent, green. Capsule 6–8 mm, light green, glabrous, ca. 2–2.5 times longer than calyx, slightly unequal, divergent, arcuately curved. Seeds numerous, brown, suborbicular, minutely papillose, with 18–23 longitudinal rows of large, thick-walled, 0.7–0.8×0.6–0.7 mm, densely located tubercles. Tubercles almost cylindrical, with one, rarely two papillae.

Phenology: The flowering period of C. fallax occurs from early to late May and the fruiting period occurs from early to late June.

Specimens examined: China, Jilin Province, Yanji City, Yanbian County, 42°59′12″N, 129°16′50″E, 300 m, 29 May 2021, H. Liu et X. T. Chen 20210529001 (HSN).

Distribution and habitat: The species C. fallax is currently known from the Russian Far East and China(Jilin). In China, it has only been observed in limited areas of Yanji. The species grows in broad-leaf forests in moist and damp areas on gentle slopes along river valleys and streams, with an elevational range of 20–380 m.

Phylogenetic position: Phylogenetic analyses indicated that C. fallax belongs to Chrysosplenium sect. Oppositifolia and forms a strongly supported clade with C. macrospermum Y. l. Kim & Y. D. Kim, C. pilosum Maxim. var. valdepilosum, C. lectus-cochleae kitagawe, C. aureobracteatum Y. l. Kim & Y. D. Kim, C. pilosum Maxim., and C. album Maxim. (Fig. 2). These species, which belong to ser. Pilosa Maxim., are primarily distributed in northeastern China, Russian Far East, Japan, and North and South Korea.

Discussion

Phylogenetic trees were constructed for 45 species of Chrysosplenium using the ML and BI approaches. The resulting topologies from both methods were similar, confirming the monophyletic nature of the genus Chrysosplenium, as supported by previous research^{[2, 3, 22]}. Our results further revealed that Chrysosplenium could be divided into three major clades, with C. microspermum positioned at the base of the phylogenetic tree, consistent with prior findings^[22]. Phylogenetic analysis also demonstrated that C. fallax belongs to Chrysosplenium sect. Oppositifolia and clusters with six other species within ser. Pilosa, which contains around 20 species^{[8, 14]}. Morphologically, C. fallax is characterized by erect sepals, opposite leaves, and pilose stems, which align with the features of ser. Pilosa^{[8, 14]}. Geographically, C. fallax has been found in the Russian Far East and Jilin Province in northeast China, corresponding to the primary distribution of ser. Pilosa in northeast Asia^{[8, 14]}. Although C. fallax and C. pilosum are not phylogenetically closely related, they share significant morphological similarities. Notably, C. fallax can be distinguished from C. pilosum by vegetative shoots lacking branching in distal part, with larger acervate leaves on top, pubescent on abaxial side of leaf blade. Additionally, C. fallax is morphologically similar to C. villosum, a species not included in our phylogenetic tree, but can be distinguished based on plagiotropic rhizome with long internodes and specialized underground stolons. Currently, five species in ser. Pilosa have been discovered in China, including C. fallax, C. pilosum, C. macrospermum, C. hebetatum, and C. lectus-cochleae. The discovery of C. fallax has expanded the distribution range of ser. Pilosa and enriched the background data on Chrysosplenium in China.