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A new species of Fordiophyton (Sonerileae, Melastomataceae) from Yunnan, China
expand article infoJin-Hong Dai, Qiu-Jie Zhou, Zhi-Yong Yu§, Ren-Chao Zhou, Ying Liu
‡ Sun Yat-sen University, Guangzhou, China
§ Management Bureau of Fenshuiling National Nature Reserve, Jinping, China
Open Access

Abstract

Fordiophyton jinpingense (Melastomataceae; Sonerileae), a species occurring in south-eastern Yunnan, China, is described as new, based on morphological and molecular data. Phylogenetic analyses, based on nrITS sequence data, showed that, except F. breviscapum, all species sampled in Fordiophyton formed a strongly supported clade in which two geographical lineages were recovered. The generic placement of F. jinpingense is well supported by phylogenetic analyses and a character combination of 4-merous flowers, distinctly dimorphic stamens and the connectives basally not calcarate. Molecular divergence and morphological evidence indicate that F. jinpingense is well separated from other members of the genus, thus justifying its recognition as a distinct species. Fordiophyton jinpingense is phylogenetically closest to F. repens, but differs markedly from the latter in stem morphology (short, obtusely 4-sided vs. long, 4-angular), habit (erect vs. creeping), leaf size (6–16.5 × 4.5–13 cm vs. 4–7.5 × 4–6.5 cm) and flower number per inflorescence (5–13 vs. 3–6).

Keywords

Fordiophyton, Melastomataceae, taxonomy, phylogeny

Introduction

In the study of Asian Sonerileae, Stapf established two new genera, Fordiophyton Stapf and Gymnagathis Stapf, based on three species in China (Stapf 1892). Both genera were accepted by subsequent authors (Krasser 1893; Diels 1932; Li 1944; Chen 1984a, b). Li (1944) pointed out that Gymnagathis is an illegitimate generic name and proposed a new name Stapfiophyton Li to replace it. However, Hansen (1992) considered the type species of Stapfiophyton, S. peperomiifolium (Oliver) H. L. Li, to be similar to Fordiophyton and therefore placed Stapfiophyton in synonymy under Fordiophyton. Hansen’s treatment was thereafter adopted by other authors (Deng and Wu 2004; Chen and Renner 2007).

Fordiophyton, as currently defined, is a small Asian genus of 13 species mainly occurring in southern China, with only one species extending to northern Vietnam (Chen and Renner 2007; Ning and Liu 2010; Zeng et al. 2016a, b). It is characterised by 4-merous flowers, eight unequal stamens, distinctly dimorphic anthers, connectives not calcarate at the base and anther base of longer stamens not forked, obtusely forked or forked and curved (Fig. 1). Ten species of Fordiophyton have been included in previous molecular phylogenetic studies (Zeng et al. 2016a, b; Zhou et al. in press). Amongst the species sampled in Fordiophyton, F. breviscapum (C. Chen) Y. F. Deng & T. L. Wu appeared to be close to Phyllagathis tetrandra Diels and P. elattandra Diels (Zhou et al. in press), while the remaining species, including the type species, F. faberi Stapf, formed a well-supported clade close to Blastus, Bredia-Phyllagathis clade 2 and Plagiopetalum (Zeng et al. 2016a, b; Zhou et al. in press).

Figure 1. 

Flowers of Fordiophyton showing anther morphology of the longer stamens. A F. peperomiifolium from Qingyuan, Guangdong, China, anther base not forked B F. faberi from Hengshan, Hunan, China, anther base forked C F. strictum from Pingbian, Yunnan, China, anther base forked and curved. Arrows indicate the anther base of the longer stamens.

During a field survey, we encountered a distinct plant in the forests of Ma-an-di, Fenshuiling National Nature Reserve in Jinping County, south-eastern Yunnan. This plant had eight distinctly dimorphic stamens and connectives not calcarate at the base, which are typical characteristics of Fordiophyton. It was distinct from all known species of Fordiophyton in the combination of short stems with distinct internodes, basal rosette of leaves, unwinged, densely villous petioles, umbellate inflorescence and anther base of longer stamens distinctly forked and curved (Figs 2, 3). We suspected that it represented an undescribed species.

To evaluate the specific status and phylogenetic position of this species in Fordiophyton, phylogenetic analyses were performed, based on DNA sequence data of the nuclear ribosomal internal transcribed spacer (nrITS). The results confirmed our suspicions that these plants represented a previously unrecognised species, F. jinpingense, which we describe below as new. A key to separate it from other species of Fordiophyton is also provided.

Figure 2. 

Fordiophyton jinpingense, all from Y. Liu 728 (SYS, A). A Habitat B a flowering individual C adaxial leaf surface D abaxial leaf surface E petiole villous with multiseriate hairs F young inflorescence G young inflorescence dissected showing the position and morphology of bracts. Scale bar: 2 cm (G).

Figure 3. 

Detail of inflorescence, flower, stamens, ovary and fruit of Fordiophyton jinpingense, all from Y. Liu 728 (SYS, A). A Mature inflorescence B side view of a flower C top view of a flower D longitudinal section of a flower showing dimorphic stamens and ovary crown E anther morphology in detail F transection of ovary at young fruit stage, showing the very short-stalked, nearly sessile placenta G young fruit showing the crown not exserted from hypanthium. Scale bars: 5 mm (D–F).

Materials and methods

For phylogenetic analyses, the nrITS sequences of F. longipes and F. jinpingense were newly sequenced, while the sequences of other species were downloaded from GenBank. The final dataset contained 131 accessions representing 106 species and three varieties from 19 genera in Sonerileae/Dissochaeteae and one in tribe Blakeeae. Blakea schlimii (Naudin) Triana was selected as an outgroup according to previous studies (Clausing et al. 2000; Clausing and Renner 2001; Renner et al. 2001; Goldenberg et al. 2012; Zhou et al. in press). In total, twelve species of Fordiophyton (85.7%) were sampled in the analyses. The source of the materials and GenBank accession numbers are given in Suppl. material 1.

Total DNA was extracted from fresh leaves using the modified CTAB procedure (Doyle and Doyle 1987). The nrITS region of F. longipes and F. jinpingense were amplified and sequenced using universal primers (White et al. 1990), following the procedure described in Zou et al. (2017).

Sequences were aligned using SeqMan v.7.1.0 (DNASTAR Inc., Madison, WI). The best-fitting nucleotide substitution model was determined using the Akaike Information Criterion in Modeltest version 3.7 (Posada and Crandall 1998) prior to phylogenetic analyses. The substitution model GTR+I+G was selected. Bayesian Inference (BI), Maximum Likelihood (ML) and Maximum Parsimony (MP) analyses were performed according to Zhou et al. (in press).

Results

The aligned sequence matrix contained 766 characters. Statistics of sequences sampled are summarised in Suppl. material 2. Trees generated by ML, MP and BI analyses were highly similar in topology, except that some nodes with weak support in ML analyses collapsed in MP or BI analyses. The tree resulting from ML analysis is shown in Suppl. material 3, with BI posterior probability (PP), ML bootstrap support values (BS) and MP bootstrap support values (PBS) labelled at nodes. As shown in Fig. 4, F. breviscapum, P. tetrandra and P. elattandra comprised a clade with weak support (PP = 0.72, BS = 42%, PBS = 49%), while the remaining 11 species formed the well-supported Fordiophyton clade (PP = 1.0, BS = 100%, PBS = 99%). The sister relationship of these two clades was only weakly supported in BI and ML analyses (PP = 0.19, BS= 15%). Two subgroups were recovered within the Fordiophyton clade with strong support. One subgroup included seven species, namely F. brevicaule C. Chen, F. chenii S. Jin Zeng & X. Y. Zhuang, F. cordifolium C. Y. Wu ex C. Chen, F. faberi, F. huizhouense S. Jin Zeng & X. Y. Zhuang, F. peperomiifolium (Oliv.) C. Hansen and F. zhuangiae S. Jin Zeng & G. D. Tang (PP = 1.0, BS = 100%, PBS = 100%); the other contained F. longipes Y. C. Huang, F. repens Y. C. Huang, F. strictum Diels and the new species, F. jinpingense (PP = 1.0, BS = 90%, PBS = 93%) (Fig. 4).

Figure 4. 

Phylogenetic relationships amongst species of Fordiophyton. Part of the Maximum Likelihood (ML) phylogenetic tree based on nrITS sequence data. Numbers above branches are bootstrap values obtained from maximum likelihood analyses, and those below branches are Bayesian posterior probabilities (right) and bootstrap values (left) resulting from maximum parsimony analyses. Box denotes the new species; asterisk denotes a branch collapsed in Bayesian inference or maximum parsimony analyses.

Discussion

Phylogeny of Fordiophyton

Phylogenetic analyses recovered two subclades in the Fordiophyton clade (Fig. 4). The grouping of species shows weak correlation with morphology. Both subclades are quite variable in habit (short stem with a basal rosette of leaves/long and leafy stem) and morphology of the leaf blade (ovate, cordate to lanceolate), petiole (hairy/glabrous, winged/unwinged) and inflorescence (umbellate/cymose paniculate). However, the subclades represent two geographic lineages. Six out of the seven species in subclade 1 are narrowly endemic to south-eastern China (Guangdong and Hongkong), whereas three out of the four species in subclade 2 are endemics of south-western China (Yunnan).

The currently circumscribed Fordiophyton is not monophyletic, as F. breviscapum appears to be related to Phyllagathis tetrandra and P. elattandra, rather than to other members of the same genus. Fordiophyton breviscapum is morphologically most closely related to F. degeneratum (C. Chen) Y. F. Deng & T. L. Wu, which was not included in the phylogenetic analyses. These two species, as well as P. tetrandra and P. elattandra, have been treated in Stapfiophyton (Li 1944; Chen 1984a, b). Interestingly, these four species share some common features, such as hypanthium distinctly 4-sided and the inner whorl of stamens greatly reduced (F. breviscapum), sterile (F. degeneratum and P. elattandra) or undeveloped (P. tetrandra) (Fig. 5). As the relationships amongst these species are only weakly supported, their generic placement remains unclear, pending further study.

Fordiophyton damingshanense S. Y. Liu & X. Q. Ning is another species which was not sampled in previous and present phylogenetic studies. It highly resembles F. faberi in habit, leaf morphology and stamen morphology. Geographically, it occurs in Guangxi, where F. faberi also occurs. Morphology and distribution imply that F. damingshanense is probably a member of subclade 1.

Figure 5. 

Stamen number and morphology of Fordiophyton breviscapum, Phyllagathis elattandra and P. tetrandra. A F. breviscapum from Ruyuan, Guangdong, China, 8 stamens with the shorter stamens greatly reduced B P. elattandra from Guiping, Guangxi, China, 8 stamens with the shorter stamens sterile C P. tetrandra from Xichou, Yunnan, China, 4 stamens. Arrows indicate anther of the shorter stamens.

Phylogenetic position and specific status of F. jinpingense

The generic placement of F. jinpingense is supported by morphological and phylogenetic data. Its 4-merous flowers, eight distinctly dimorphic stamens and the connectives basally not calcarate fit perfectly well with the morphological circumscription of Fordiophyton. Phylogenetic analyses also showed that F. jinpingense was nested within the same clade, together with the type of Fordiophyton, F. faberi.

At the molecular level, pairwise sequence divergence at the nrITS region between F. jinpingense and other species of Fordiophyton ranges from eight to 42 nucleotide substitutions, which is equivalent to the number of substitutions between other species of Fordiophyton (ranging from 14 to 47 nucleotide substitutions). Molecular divergence, therefore, indicates that F. jinpingense is well diverged from other members of the genus. Morphologically, the basal rosette of leaves of F. jinpingense makes it quite distinct from species with erect, leafy stems, viz. F. cordifolium, F. faberi, F. longipes and F. strictum. It closely resembles F. brevicaule, F. chenii, F. huizhouense, F. peperomiifolium and F. zhuangiae in habit, but differs from F. chenii and F. zhuangiae in the unwinged, villous petioles (vs. winged and glabrous), from F. huizhouense and F. peperomiifolium in stems with distinct internodes (vs. indistinct) and from F. brevicaule in longer petioles (3–16 cm vs. 1–3 cm), larger leaf blades (6–16.5 × 4.5–13 cm vs. 3.5–8 × 2–5 cm) and umbellate inflorescence (vs. cymose paniculate). In fact, the phylogenetic analyses showed that F. jinpingense is most closely related to F. repens rather than to the above species. Fordiophyton repens is narrowly endemic to Pingbian County, south-eastern Yunnan. The two are similar in having villous petiole and leaf blade, umbellate inflorescence and anther base of longer stamens forming a forked spur. Nevertheless, they differ markedly in stem morphology (short, obtusely 4-sided vs. long, 4-angular), habit (erect vs. creeping) (Fig. 6), leaf size (6–16.5 × 4.5–13 cm vs. 4–7.5 × 4–6.5 cm) and flower number per inflorescence (5–13 vs. 3–6). Therefore, both molecular and morphological evidence justify the recognition of F. jinpingense as a distinct species.

Figure 6. 

A Y. Y. Hu and S. K. Wen 580300 (KUN) collected from Pingbian County, Yunnan, China, holotype of Fordiophyton repens B Y. Liu 728 (A) collected from Ma-an-di, Jinping County, Yunnan, China, holotype of Fordiophyton jinpingense.

Taxonomic treatment

Fordiophyton jinpingense J.H.Dai & Z.Y.Yu, sp. nov.

Figures 2, 3

Type

CHINA. Yunnan: Jinping County, Ma-an-di town, 900–1900 m alt., damp but well drained places in forest, 10 Mar 2019, Ying Liu 728 (holotype: A; isotype: SYS).

Diagnosis

Differs from F. repens in having slightly obtusely 4-sided short stem (vs. 4-angular, long and creeping), mature leaves 6–16.5 × 4.5–13 cm (vs. 4–7.5 × 4–6.5 cm) sparsely and shallowly dentate leaf margin with each tooth having a caducous terminal seta (vs. densely denticulate, persistent) and inflorescence 5–13-flowered (vs. 3–6-flowered).

Description

Perennial herbs, 10–14 cm tall (including inflorescence). Stems 2–5 cm long, slightly obtusely 4-sided, sometimes branched, villous with multiseriate hairs. Petiole 3–16 cm long, densely villous with multiseriate hairs; leaf blade ovate-oblong to ovate-orbicular, 6–16.5 × 4.5–13 cm, papery, adaxially green to dark green, abaxially pale green or sometimes purplish-red, villous with multiseriate hairs on veins, both surfaces inconspicuously pubescent with very short, appressed uniseriate hairs, secondary veins 3 or 4 on each side of midvein, base cordate, margin sparsely and shallowly dentate with each tooth having a terminal seta when young but caducous at maturity, apex short acute, obtuse or retuse. Inflorescences terminal and axillary, umbellate, 5–13-flowered; peduncle 9–14 cm long, sometimes white maculate, bearing several multiseriate hairs at nodes, otherwise glabrous; bracts caducous, oblong, 1–3 cm long, one pair (rarely two) in middle or lower part and another two pairs enclosing the flowers. Pedicels 4–10 mm long, glabrous. Hypanthium funnel-shaped, ca. 10 mm long, obtusely 4-sided, glabrous. Calyx lobes narrowly triangular-ovate, 2–5 × 1–2 mm, margin entire, apex obtuse or acute, caducous. Petals pink, obovate, ca. 16 × 8 mm, oblique. Longer stamens pink; filaments ca. 9 mm; anthers ca. 13 mm long, linear, curved, base lengthened into a forked, curved spur, connective bulging basally. Shorter stamens yellowish; filaments ca. 6 mm long; anthers oblong, 3–4 mm long, base obtusely forked, connective base slightly bulging. Ovary obovate, apex with a membranous ciliate, 4-lobed crown. Capsule funnelform-campanulate, ca. 6 mm in diam., apex 4-lobed, crown not exserted from calyx; hypanthium exceeding capsule, glabrous. Seeds numerous.

Phenology

Flowering March–April, fruiting April–May.

Etymology

The specific epithet is derived from Jinping County, the type locality of Fordiophyton jinpingense.

Distribution

Fordiophyton jinpingense is currently known only from Jinping County, south-eastern Yunnan, China (Fig. 7). It occurs in dense or open forests, often in damp, shaded, but well drained places, such as on steep slopes, at 900–1900 m alt.

Figure 7. 

Distribution of Fordiophyton jinpingense.

Key to the species of Fordiophyton

1 Leaves in a basal or sub-basal rosette 2
Leaves cauline 7
2 Petiole winged and glabrous 3
Petiole unwinged, densely or sparsely hairy 4
3 Petioles 8–18 cm long; leaf blade 9–13 × 9–12 cm; secondary veins 4 on each side of midvein; hypanthium and calyx lobes hairy F. chenii
Petioles 2–4 cm long; leaf blade 4–9 × 2–4 cm; secondary veins 2 or 3 on each side of midvein; hypanthium and calyx lobes glabrous F. zhuangiae
4 Internodes of stems distinct 5
Internodes of stems indistinct 6
5 Internodes glabrous; petioles 1–3 cm long; leaf blade 3.5–8 × 2–5 cm; inflorescence cymose-paniculate; anthers of longer stamens forming an obtuse forked spur at base F. brevicaule
Internodes hairy; petioles 3–16 cm long; leaf blade 6–16.5 × 4.5–13 cm; inflorescence umbellate; anthers of longer stamens forming a forked, curved spur at base F. jinpingense
6 Hypanthium glabrous; calyx lobes lanceolate, 6 × 2 mm; base of connective of longer stamens prolonged F. huizhouense
Hypanthium sparsely hairy; calyx lobes triangular, 1 × 2 mm; base of connective of longer stamens not prolonged F. peperomiifolium
7 Stem creeping F. repens
Stem erect or at least erect in upper part 8
8 Stem less than 20 cm long 9
Stem more than 30 cm long 10
9 Stem winged; secondary veins 1 on each side of midvein; inner 4 stamens fertile F. breviscapum
Stem not winged; secondary veins 3 or 4 on each side of midvein; inner 4 stamens sterile F. degeneratum
10 Leaves of a pair highly unequal and asymmetric; petioles often less than 1 cm long; bracts cordate, ca. 4 mm long F. strictum
Leaves of a pair equal or slightly unequal; petioles more than 2 cm long; bracts more or less ovate, often more than 1 cm long 11
11 Leaf blade cordate to ovate-cordate, secondary veins 4 or 5 on each side of midvein F. cordifolium
Leaf blade broadly lanceolate, oblong, ovate, oblong-lanceolate to elliptic; secondary veins 2 or 3, rarely 4 (F. damingshanense) on each side of midvein 12
12 Inflorescences umbellate, peduncle winged F. longipes
Inflorescences cymose-paniculate, umbellate or a pleiochasium, peduncle not winged 13
13 Inflorescences cymose-paniculate, umbellate, 13–20 cm long F. faberi
Inflorescences pleiochasia, ca. 10 cm long F. damingshanense

Acknowledgements

We thank Ms. Xiao-Lan Wang for providing the photo of F. faberi, Dr. David E. Boufford for his valuable comments on the manuscript and the staff of Fenshuiling National Nature Reserve for their help in the field. This work was supported by the National Natural Science Foundation of China (31770214) and the Science and Technology Planning Project of Guangdong Province (2015A030302011).

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