Research Article |
Corresponding author: Nian-He Xia ( nhxia@scbg.ac.cn ) Academic editor: Marcelo Reginato
© 2022 Si-Jin Zeng, Yi-Hua Tong, Nian-He Xia.
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:
Zeng S-J, Tong Y-H, Xia N-H (2022) Fordiophyton tereticaule (Melastomataceae), a new species from China. PhytoKeys 197: 59-69. https://doi.org/10.3897/phytokeys.197.82670
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A new species, Fordiophyton tereticaule, from China, is described and illustrated here based on morphological and molecular evidence. It is morphologically similar to F. faberi in having erect stems, slightly oblique and membranous leaf blades, broadly ovate to suborbicular bracts, and oblong petals, but differs by the terete stems, densely puberulous petioles, and elliptic leaf blades. Our phylogenetic analyses based on plastid genome and nrITS data indicate that this new species is clustered with four Fordiophyton species of Yunnan but placed far apart from F. faberi. An updated key to the genus is also provided.
phylogeny, Sonerileae, taxonomy, Yunnan
Fordiophyton Stapf, a genus belonging to the tribe Sonerileae of the family Melastomataceae, is endemic to China and Vietnam with 15 species currently known (
During a recent survey in Malipo County, Yunnan Province, China in November 2019, we encountered an interesting Fordiophyton species with terete stems. At first glance, it looked like another two species also occurring in Yunnan, viz. F. faberi Stapf or F. strictum Diels because of its erect stems and membranous leaf blades, but those two species have very different quadrangular stems.
After careful examination of specimens of Fordiophyton species from China and Vietnam, and referring to the relevant references (
A total of 43 species from 13 genera (including 14 species of Fordiophyton) in the Sonerileae were sampled (Suppl. material
Silica-gel dried leaves of this unknown species were sent to Novogene (Tianjin, China) to extract total genomic DNA for library (350 bp) preparation for genome skimming sequencing. Paired-end (150 bp) sequencing was conducted on Illumina NovaSeq 6000 (San Diego, CA, USA), generating ca. 20 Gb raw data. After quality control of the raw data by fastp v.0.23 (
All plastid genome sequences were aligned by MAFFT v.7.4 (FFT-NS-i × 1000 strategy) after removing one inverted repeat region of each sample (
The aligned plastid genome matrix contained 140 425 bp, of which 13 003 bp (9.26%) are variable and 3 790 bp (2.70%) are parsimony informative. The aligned nrITS matrix contained 724 bp, of which 324 bp (44.75%) are variable and 216 bp (29.83%) are parsimony informative. The best-fit model (TVM+F+R3) for plastid genome matrix and best-fit model (GTR+F+I+G4) for nrITS matrix were automatically chosen by IQTREE according to Bayesian Information Criterion. The phylogenetic analysis based on the plastid genome (Fig.
The phylogenetic analyses confirmed that Fordiophyton is polyphyletic and consists of two clades (
Morphologically, the unknown species is more similar to F. faberi than any other Fordiophyton species in both vegetative and reproductive characters, such as the erect stems, long petioles, slightly oblique and membranous leaf blades, broadly ovate to suborbicular bracts, and non-auriculate base of the calyx lobes. But the phylogenetic analyses revealed the unexpected placement of the unknown species in a different subclade from F. faberi (as shown in Fig.
Morphological comparison of key features among Fordiophyton tereticaule, F. faberi and F. strictum.
Characters | F. tereticaule | F. faberi | F. strictum |
---|---|---|---|
Stem | terete, with dense glandular trichomes and puberulous when young, becoming glabrescent | quadrangular, glabrous | quadrangular, glabrous, usually pilose or setose at nodes |
Petioles | 1–7 cm long, densely puberulous | 1.5–7 cm long, glabrous or shortly setose near leaf blade | usually less than 0.8 cm long, glabrous |
Leaf blades | elliptic, slightly oblique | broadly lanceolate, oblong, ovate, or rarely lanceolate, slightly oblique | broadly lanceolate, oblique |
Bracts | broadly ovate to suborbicular | broadly ovate to suborbicular | cordate |
Calyx lobes | triangular to ovate-triangular without auriculate base | triangular to lanceolate-triangular without auriculate base | broadly ovate-triangular with auriculate base |
Longer stamens | anther base lengthened into a forked and curved spur | anther base lengthened into a forked spur | anther base lengthened into a forked and curved spur |
In Clade B, F. breviscapum is sister to Blastus with strong support (SH-aLRT 100%, UFBoot 100%) but far apart from two species of Kerriothyrsus C.Hansen Clade (Fig.
China. Yunnan: Wenshan Zhuang and Miao Autonomous Prefecture, Malipo County, Laojunshan Provincial Nature Reserve, elev. 1517 m, 18 September 2020 (fl.), Si-Jin Zeng 4932 (holotype: IBSC!; isotypes: CANT!, KUN!, PE!).
Fordiophyton tereticaule S.Jin Zeng & N.H.Xia A fruiting branch B part of stem with one petiole C part of leaf blade, adaxial view D cymose inflorescence with opening flowers E calyx lobe F petal G longer stamen, front view (left) and side view (right) H shorter stamen, front view (left) and back view (right). Drawn by Ding-Han Cui.
Similar to F. faberi in having erect stems, membranous leaf blades, and oblong petals, but differs by the terete (vs. quadrangular) stems, densely puberulous (vs. green and glabrous or shortly setose near leaf blade base) petioles, and elliptic (vs. broadly lanceolate, oblong, ovate, or rarely lanceolate) leaf blades.
Fordiophyton tereticaule S.Jin Zeng & N.H.Xia A flowering plants B part of stem with a pair of petioles C a pair of leaves D cymose inflorescence with flower buds E cymose inflorescence, oblique view F an opening flower, front view G an opening flower, side view H infructescence, side view I young fruits, top view.
Herbs, 30–100 cm tall. Stems yellowish-green when young, turning red, terete, with dense glandular trichomes and puberulous when young, becoming glabrescent, inflated at the nodes. Leaves in unequal pairs in size; petiole reddish brown, terete, 1–7 cm long, densely puberulous; leaf blade elliptic, slightly oblique, 8–16 × 4–9 cm, membranous, base cordate, apex acuminate to caudate-acuminate, margin inconspicuously serrulate with each tooth bearing a terminal seta, adaxial surface yellowish-green, sparsely puberulous, abaxial surface yellowish-green, densely puberulous on veins; secondary veins 2–3 on each side of midvein, conspicuous; tertiary veins numerous, parallel, connecting with secondary veins. Inflorescences terminal, an umbel-like cyme, sometimes a thyrse, with 6–15 flowers; peduncle usually dull red, terete, 1.3–3.5 cm long, with dense red glandular trichomes; bracts yellowish-green to dull red, imbricate at base of pedicel, broadly ovate to suborbicular, with sparse red glandular trichomes, caducous. Pedicel dull red, terete, 3–5 mm long, with dense red glandular trichomes. Hypanthium scarlet, funnel-form, 6–8 × 3–4 mm, with dense red glandular trichomes. Calyx lobes dull red to scarlet, triangular to ovate-triangular, ca. 5 × 2–4 mm, with sparse red glandular trichomes, apex obtuse to acute, base not auriculate. Petals white to pinkish, oblong, ca. 1.1 × 0.5–0.6 cm, apex oblique with 1 glandular trichome at tip. Stamens 8, 4 longer antisepalous ones and 4 shorter antipetalous ones, arranged in 2 whorls. Antisepalous (longer) stamens 2.0–2.5 cm long; filaments 0.9–1.4 cm; anthers dull red, linear, ca. 1.1 cm long, curved, base lengthened into a forked, curved spur, connective base inflated. Antipetalous (shorter) stamens 0.9–1.2 cm long; filaments 0.6–0.9 cm; anthers yellow, ovoid, ca. 0.3 cm long, straight, connective base slightly inflated. Style 1.7–2.0 cm long, glabrous or with sparse glandular trichomes at base. Ovary half-inferior, ovoid, apex with a membranous crown. Capsule funnel-form, ca. 8 × 4 mm; placentation axillary, placentas shortly stalked; seeds more than 100, cuneate, less than 2 mm long.
Flowering in September-December, fruiting in October–next January.
Fordiophyton tereticaule is only known from Malipo County, Yunnan, China. It grows in broad-leaved evergreen forests at elevations of 1260–1540 m.
The specific epithet refers to the terete stem.
China. Yunnan: the same locality as above, 1516 m, 28 November 2019, Si-Jin Zeng 898 (paratypes: IBSC!).
1 | Internodes of stems indistinct, less than 2 mm | 2 |
– | Internodes of stems distinct, more than 5 mm | 6 |
2 | Stem glabrous; petioles winged | 3 |
– | Stem densely hirsute or setose; petioles unwinged | 4 |
3 | Petioles 8–18 cm long; leaf blades ovate or ovate-elliptic, 9–13 × 9–12 cm | F. chenii |
– | Petioles 2–4 cm long; leaf blades elliptic, 4–9 × 2–4 cm | F. zhuangiae |
4 | Leaf blades with minute brown glands on both surfaces | F. phamhoangii |
– | Leaf blades without minute brown glands on both surfaces | 5 |
5 | Adaxial surface of leaf blades glabrous; calyx lobes lanceolate, ca. 6 mm long | F. huizhouense |
– | Adaxial surface of leaf blades tuberculate; calyx lobes triangular, 1–2 mm long | F. peperomiifolium |
6 | Leaves in a sub-basal rosette | 7 |
– | Leaves cauline, not in a rosette | 9 |
7 | Petioles densely villous | F. jinpingense |
– | Petioles glabrous or sparsely glandular-setose | 8 |
8 | Stem winged, glabrous at nodes; petioles glabrous; secondary veins 4 or 5 on each side of midvein | F. cordifolium |
– | Stem unwinged, densely spiny at nodes; petioles sparsely glandular-setose; secondary veins 3 on each side of midvein | F. brevicaule |
9 | Stem creeping | F. repens |
– | Stem erect or at least erect in the upper part | 10 |
10 | Leaves of a pair highly unequal (smaller one less than half of larger one’s size); petioles often less than 1 cm long; base of calyx lobes auriculate | F. strictum |
– | Leaves of a pair not unequal or only slightly unequal; petioles often more than 2 cm long; base of calyx lobes not auriculate | 11 |
11 | Plants less than 25 cm tall; anthers of antipetalous stamens greatly reduced or sterile | 12 |
– | Plants more than 30 cm tall; anthers of antipetalous stamens fertile, not greatly reduced | 13 |
12 | Stem winged; secondary veins 1 on each side of midvein | F. breviscapum |
– | Stem unwinged; secondary veins 3 or 4 on each side of midvein | F. degeneratum |
13 | Stem terete; petioles densely puberulous | F. tereticaule |
– | Stem quadrangular; petioles glabrous or shortly setose near leaf blade base | 14 |
14 | Abaxial surface of leaf blades furfuraceous; peduncle winged | F. longipes |
– | Abaxial surface of leaf blades glabrous or minutely puberulous; peduncle unwinged | 15 |
15 | Inflorescence an umbel-like cyme or a thyrse; anther base of longer stamens not enlarged | F. faberi |
– | Inflorescence a pleiochasium; anther base of longer stamens enlarged | F. damingshanense |
We thank Mr Xi-Bing Guo for his kind assistance with our field survey and Mr Ding-Han Cui for the beautiful line-drawing. This study was funded by Guangzhou Science and Technology Project no. 202102021219.
Table S1. Vouchers and Genbank accession numbers of the samples used in this study
Data type: docx file
Explanation note: Dashes (–) indicate missing data, and asterisks (*) denote the sequence obtained in this study.
Figure S1. Phylogenetic relationships of Sonerileae based on nrITS
Data type: JPG file
Explanation note: The numbers near the nodes are the values of the SH-aLRT test (left) and ultrafast bootstrap (right). The unknown species is indicated by an asterisk.