Research Article |
Corresponding author: Ying Liu ( liliumrosa@163.com ) Academic editor: Ricardo Kriebel
© 2020 Jin-Hong Dai, Qiu-Jie Zhou, Ren-Chao Zhou, Ying Liu.
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:
Dai J-H, Zhou Q-J, Zhou R-C, Liu Y (2020) A new species of Bredia (Sonerileae, Melastomataceae) from Sichuan, China. PhytoKeys 152: 1-14. https://doi.org/10.3897/phytokeys.152.53512
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Bredia hispida (Sonerileae, Melastomataceae), a species occurring in southeastern Sichuan, China, is newly described based on morphological and molecular data. The generic placement of B. hispida is well supported by phylogenetic analysis and morphological characters, including basally cordate, hairy leaf blade, cymose inflorescence, basally gibbous anthers and enlarged ovary crown enclosing an inverted frustum-shaped depression. Both molecular and morphological divergence showed that B. hispida is well separated from its close relatives, justifying its recognition as a distinct species. The new species resembles B. repens, B. changii and B. guidongensis in the prostrate habit and isomorphic stamens but differs markedly in the unequal opposed leaves, the 2–4 mm long, stout bristles on the adaxial surface of leaf blade and acuminate leaf apex. Bredia hispida co-occurs with B. esquirolii in the wild. No morphologically putative hybrids between them were observed despite their overlap in flowering season. The isolating mechanism remains unclear, pending further investigation.
Bredia, Melastomataceae, phylogeny, taxonomy
Bredia Blume was originally established based on B. hirsuta Blume, a species endemic to Taiwan and the Ryukyu islands (
During a survey of specimens in Chinese herbaria for a project on species delimitation of Bredia, several collections from Xuyong County, southeastern Sichuan Province, caught our attention. These collections (e.g. Fig.
Herbarium specimen of Bredia hispida (A–C) and Phyllagathis deltoidea (D–F). A–C W. B. Ju and H. N. Deng, HGX12702 (CDBI) collected from Shui-wei town, Xuyong County, Sichuan, China, showing the stout long bristles on adaxial surface of the leaf blade and linear-lanceolate calyx lobes, images from National Plant Specimen Resource Center D–F H. H. Su 68119 (IBK, IBSC) collected from Aidian, Ningming County, Guangxi, China, holotype (IBSC) (D, F) and isotype (IBK) (E) of Phyllagathis deltoidea.
In September 2019, we made a field expedition to Xuyong County and collected flowering and fruiting specimens of the plant in question (Figs
To test the generic affiliation of the unknown plant and its closest relative in the genus, we performed phylogenetic analyses based on DNA sequence data of nuclear ribosomal internal transcribed spacer (nrITS), sampling all species so far recorded in Bredia. We also calculated pairwise genetic distances among this plant and 23 species of Bredia to evaluate its distinctness. The results confirmed our suspicion that this plant represented a species new to science, which we described as B. hispida below.
Floral details and young fruit of Bredia hispida. A Side view of a flower B top view of a flower C longitudinal section of a flower showing isomorphic stamens and ovary crown D top view of a young fruit E side view of a young fruit showing enlarged ovary crown exserted from hypanthium. Scale bar: 5 mm (C). All from Y. Liu 764 (A, PE, SYS).
To test the generic affiliation of B. hispida and its position in the genus, we selected ingroup taxa based on previous studies (
Total DNA was extracted from fresh leaves using the modified CTAB procedure (
Sequences were aligned using SeqMan v.7.1.0 (DNASTAR Inc., Madison, WI). The Akaike information criterion in Modeltest version 3.7 (
The aligned sequence matrix contained 665 characters. Statistics of sequences sampled were summarized in Supplementary material
The placement of B. hispida in Bredia is supported by phylogenetic and morphological data. Our phylogenetic analyses with complete taxon sampling of Bredia confirmed that B. hispida is a member of this clade. Morphologically, its basally cordate, hairy leaf blade, cymose inflorescence, two whorls of eight isomorphic stamens, basally slightly gibbous anthers, decurrent connectives, and enlarged ovary crown during the fruiting stage all fit well within Bredia.
Bredia hispida is phylogenetically most closely related to B. repens, B. tuberculata and B. yunnanensis. It is a dwarf subshrub up to 15 cm tall with its middle and lower stem prostrate, which makes it easily distinguished from most species of Bredia, including B. tuberculata and B. yunnanensis. It closely resembles B. guidongensis (Fig.
Bredia hispida is currently only known from Xuyong County, Sichuan Province. It co-occurs with B. esquirolii (H. Lév.) Lauener, a species widely distributed in Guizhou, Chongqing and Sichuan. Bredia hispida grows on shady red sandstone cliff of seasonal waterfall whereas B. esquirolii is found in bushes, under forests and also on shady cliff (but a little further away from the dripping water). Several cases of sympatry have been observed elsewhere in the genus, viz. B. dulanica C. L. Yeh, S. W. Chung & T. C. Hsu and B. oldhamii Hook. f. in Taiwan, B. repens and B. latisepala (C. Chen) R. Zhou & Ying Liu in Hunan and B. esquirolii and B. tuberculata in Sichuan. In the first two cases, the co-occurring species have non-overlapping flowering seasons and thus interspecific reproductive isolation is easily maintained; in the third case, the flowering periods overlapped, and some putative hybrid individuals were found (unpublished data). During our visit in September 2019, both B. hispida and B. esquirolii were flowering. But no morphologically putative hybrids were observed. Pre-zygotic isolation via different pollinators is not a plausible explanation as flowers of the two species are of similar size (ca. 2 cm in diameter) and both can be visited by medium to small size bees. According to previous analyses (
Phylogenetic position of Bredia hispida. 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. The new species is noted in bold. Asterisk denotes a branch collapsed in Bayesian inference or maximum parsimony analyses.
China. Sichuan: Xuyong County, Shui-wei town, Guang-mu village, 1338 m, on steep rock cliff of a small waterfall, 1 Sept 2019, Ying Liu 764 (holotype: PE; isotype: A, SYS).
Resembles B. changii, B. repens and B. guidongensis in the prostrate habit and isomorphic stamens but differs from these species in its unequal leaves (vs. equal), stiffly papery leaf blade (vs. papery) hispid with 2–4 mm long, spreading stout bristles (vs. pubescent or villous with trichomes ≤ 1 mm) and acuminate apex (vs. obtuse or acute).
Subshrubs, up to 15 cm tall. Stems cylindrical, inconspicuously pubescent with very short, uniseriate appressed trichomes, prostrate at middle and lower parts, branched, with adventitious roots. Opposed leaves often unequal; petiole 0.6–5 cm long, inconspicuously pubescent; leaf blade ovate to ovate elliptic, larger blades 4–9.9 × 1.6–4 cm, smaller blades 1.1–5× 0.7–2.5 cm, stiffly papery, abaxial surface pale green, inconspicuously pubescent, adaxial surface green to yellowish green, inconspicuously pubescent, hispid with spreading stout white bristles (2–4 mm long) between veins, lateral veins 2 or 3 pairs, base cordate, margin inconspicuously serrulate, apex acuminate. Inflorescences terminal or axillary, sometimes on old branchlets; 2–3-flowered cyme or solitary. Peduncle 2–10 cm long, pubescent with uniseriate appressed trichomes. Flowers bisexual, radial but androecium slightly bilateral, 4-merous, rarely 5-merous. Pedicels and calyces pubescent with uniseriate appressed trichomes and multiseriate spreading glandular trichomes. Pedicels 7–16 mm long. Hypanthium cup-shaped, ca. 4 × 4 mm, pubescent with spreading glandular trichomes. Calyx lobes 4, linear-lanceolate, ca. 3–4 mm long. Petals 4, purplish pink, ovate, 7 × 5 mm, slightly oblique, apex acute. Stamens 8, isomorphic, subequal in length, 8–10 mm long. Anthers purplish, bilocular, lanceolate, ca. 4–5.5 mm long, base slightly gibbous, connective decurrent, forming a tuberculate appendage dorsally. Ovary half inferior, locules 4, placentation axillary, ovary apex with a membranous crown, crown margin ciliate with glandular trichomes. Style ca. 11 mm long, puberulous in the lower part. Young fruit cup-shaped, apex crowned, crown exserted from hypanthium. Seeds numerous, premature.
Flowering July–September, young fruits in September.
The specific epithet is based on the spreading stout bristles on the leaf blade of this species.
China. Sichuan: Xuyong County, Shui-wei town, Guan-dou village, 15 Sept 2013, W. B. Ju and H. N. Deng, HGX13524 (CDBI); Xuyong County, Shui-wei town, Guang-mu village, 27 Aug 2013, W. B. Ju and H. N. Deng, HGX12702 (CDBI); Xuyong County, Long-feng town, Ling-guan-ti power station, 4 Aug 2012, X. F. Gao, Y. D. Gao and W. B. Ju, HGX10961 (CDBI).
We thank Herbarium of Chengdu Institute of Biology (CDBI) for their kind assistance during herbarium survey. We are grateful to Dr. David E. Boufford and the anonymous reviewer for their valuable comments on the manuscript. This work was supported by the National Natural Science Foundation of China (31770214), Science and Technology Program of Sichuan Province (2018JY0487) and Science and Technology Project of Yuexiu District, Guangzhou City (2018-GX-001).
Table S1. Source of materials studied and GenBank accession numbers for nrITS
Data type: Table
Explanation note: Newly generated sequences are indicated in bold.
Table S2. Summary statistics of sequences used for phylogenetic analyses
Data type: Table
Explanation note: PIS, parsimony-informative sites.
Table S3. Pairwise genetic distances among species of Bredia at the nrITS region
Data type: Table
Explanation note: Those between B. hispida and remaining species are indicated in bold.