Research Article |
Corresponding author: Wannachai Chatan ( wannachaichatan@gmail.com ) Academic editor: Peter Bruyns
© 2020 Wilawan Promprom, Wannachai Chatan.
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:
Promprom W, Chatan W (2020) A new species of Dischidia (Apocynaceae, Asclepiadoideae) from North-eastern Thailand. PhytoKeys 144: 23-30. https://doi.org/10.3897/phytokeys.144.47977
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Dischidia phuphanensis Chatan & Promprom, a new species from north-eastern Thailand, is described and illustrated. The new species is similar to D. tonkinensis Costantin, but is distinguished by the shape of its leaves, the apices of the staminal corona lobes, the colour of the corolla and the absence of a corolline corona. The distinguishing characters of similar species are discussed. A key for the identification of those species in Thailand without pitcher-like leaves is provided.
Marsdenieae, plant diversity, taxonomy
Dischidia
Specimens were collected from Phu Pha Yol National Park, Sakon Nakhon Province, Thailand in 2017. Morphological observations of the new species were carried out on living plants from the field, as well as on herbarium specimens in BK and BKF. Measurements were made with a Vernier caliper or with an ocular micrometer in a dissecting microscope. We consulted the relevant taxonomic literature (e.g.
Dischidia phuphanensis is most similar to D. tonkinensis, but the new species differs from the latter in its elliptic or narrowly elliptic or slightly oblanceolate leaves (leaves in D. tonkinensis are ovate to ovate elliptic, rarely obovate), apex of corona lobes obtuse (with tips pointing downward in D. tonkinensis), yellow base of the corolla tube and light yellow or white apices of the lobes (white or orange-yellow corolla tube and lobes in D. tonkinensis) and the absence of a corolline corona (corolline corona present in D. tonkinensis). (Figures
Dischidia phuphanensis. A Branch with leaves and inflorescences B bud C flower D dissected flower with half of corolla removed E calyx from abaxial side F gynostegium (side view), with coronal lobes removed G gynostegium (from above) H pollinarium I pistil J pistil (style-head removed) K follicle L seed A–J drawn by Wannachai Chatan from W. Chatan 2489, and K, L from W. Chatan 2904.
Thailand: Sakon Nakhon Province, Phu Pha Yol National Park, 300–400 m, 16°56.126667'N, 104°2.336667'E, 7 August 2017, W. Chatan 2489 (holotype: BKF!; isotype: BK!).
Plant epiphytic or lithophytic, sometimes pendulous, fleshy, growing loosely rooted on the host trees or shrubs or on rocks, glabrous except in tube of corolla. Branches terete, 2.0–2.5 mm thick, green or greenish-purple; internodes 5–15 cm long. Stipular colleters paired, triangular, ca. 0.1 mm long. Leaves with cylindrical (slightly flattened above), 7–13 × 2.0–2.3 mm petiole; lamina green, dark green or purplish-green, underneath lighter green, slightly fleshy and coriaceous, elliptic, narrowly elliptic or slightly oblanceolate, 3–5 × 1.5–2.0 cm, apex acute-apiculate, base round or slightly acute, margin entire, gland present on adaxial side near lamina base, midrib and secondary veins inconspicuous on both surfaces. Inflorescences umbelliform, usually bearing 1–4 open flowers and 2–5 developing buds; bracts 2 subtending each flower, triangular, ca. 0.5 × 0.5 mm, greenish-brown, apex acute; peduncle extra-axillary or apparently axillary, persistent, 0–3 mm long; rachis 1–5 per peduncle, bearing scars of previous flowerings 1–3 × 1.0–1.8 mm; pedicels 1–2 × ± 0.5 mm. Sepals greenish-white, lobes ovate, 0.6–0.8 × 0.5–0.8 mm, apex round, without colleters. Corolla broadly urceolate or slightly globose, 2.4–2.6 × 2.4–2.5 mm, basally yellow, progressively fading into light yellow or white at the tips of the lobe, corolla tube with one ring of retrorse hairs in throat; lobes triangular to deltate, light yellow or white, 1.3–1.5 × ca. 1.3 mm, apex acute; corolline corona absent. Gynostegium conical in outline, 1.8–2.0 mm tall, 1.4–1.6 mm in diameter. subsessile; stipe ca. 0.1 mm tall. Staminal corona lobes anchor-shaped, stalk ca. 0.8 mm high, apical part ca. 0.6 × 0.8 mm, apex obtuse. Pollinarium erect, ca. 2 mm long. Pollinium yellow, 0.6–0.8 × 0.20–0.22 mm, ellipsoidal; translator arms 1.0–1.2 mm long; corpusculum ovate, reddish-brown, 0.15–0.16 × 0.05–0.07 mm. Ovary bicarpellate, bottle-shaped and slightly flattened, 0.7–1.0 mm long, each carpel ca. 0.2–0.5 mm in basal diameter. Follicles solitary by abortion. linear, 38–45 × 2.5–3.0 mm, green when immature changing to brown when ripe. Seed slightly cylindrical, 3.8–4.0 × 1.3–1.5 mm, base obconic, bearing white coma 30–32 mm long.
Thailand, Sakon Nakhon Province: Phu Pha Yol National Park, 300–400 m alt., 16°56'07.2"N, 104°02'21.1"E, 5 September 2017, W. Chatan 2904 (paratype: BKF).
Flowering in July–September and fruiting in Aug–December.
This new species grows in both slightly open and in shaded areas in mixed deciduous forest at an elevation of 300–400 m.
Thao Rag Noi.
The specific epithet of Dischidia phuphanensis refers to its type locality, the Phuphan mountain range.
One population of Dischidia phuphanensis was found at the type locality in Phu Pha Yol National Park, Sakon Nakhon Province, north-east Thailand. It is estimated to number fewer than 250 mature individuals. Therefore, it should be considered as “Endangered (EN)” according to the IUCN criteria D (
Dischidia phuphanensis is similar to D. tonkinensis, from China, Indochina and Thailand (
The genus Dischidia may be divided into two main groups based on the leaf types, i.e. those with pitcher-like leaves and species with non-pitcher-like leaves. Dischidia phuphanensis has non-pitcher-like leaves. The most recent revision of Dischidia in Thailand was by
Distinguishing features between Dischidia phuphanensis and D. tonkinensis.
Characters | D. phuphanensis | D. tonkinensis |
---|---|---|
1. Leaf shape | elliptic or narrowly elliptic or slightly oblanceolate | ovate to ovate-elliptic, rarely obovate |
2. Corolla colour outside | tube yellow at base, light yellow or white towards apices of lobes | white or orange-yellow tube and lobes |
3. Corolline corona | Absent | present |
4. Staminal corona lobes | stalked, anchor shaped with apex obtuse | stalked, anchor shaped with apex retuse |
1 | Leaves broadly ovate or orbicular or orbicular-peltate; if elliptic, then mixed with others that are peltate or orbicular | 2 |
– | Leaves narrowly ovate, elliptic, narrowly elliptic, obovate, lanceolate, oblanceolate, or spathulate; not mixed with peltate or orbicular leaves | 5 |
2 | Leaves broadly ovate or orbicular or elliptic, abaxial sides slightly flattened | D. nummularia |
– | Leaves peltate or orbicular, abaxial sides distinctly concave; | 3 |
3 | Branches pubescent | D. astephana |
– | Branches glabrous | 4 |
4 | Staminal corona lobes ± absent | D. imbricata |
– | Staminal corona lobes consisting of spreading horn-like projections | D. cornuta |
5 | Leaves abruptly laterally expanded at the middle or in upper half | D. singularis |
– | Leaves not expanded in upper half | 6 |
6 | Leaves linear or narrowly elliptic or spathulate; proportion of length /width is 3.8–16 | D. bengalensis |
– | Leaves ovate, elliptic, lanceolate, obovate, slightly oblanceolate or broadly obovate; proportion of length/width ratio smaller than 3.8 | 7 |
7 | Leaves broadly obovate, rarely elliptic; staminal corona lobes broadly saddle-shaped | D. griffithii |
– | Leaves ovate, elliptic, slightly elliptic, lanceolate, slightly oblanceolate; staminal corona lobes anchor shaped or sagittate or reduced to minute swellings | 8 |
8 | Branches pubescent, tomentose or hirsute | 9 |
– | Branches glabrous | 11 |
9 | Corolla pink, red, dark red or purple, 6–7 mm long, with two rings of hairs inside around mouth of tube | D. hirsuta |
– | Corolla white or creamy white, less than 5.5 mm long, mouth of corolla tube glabrous or with a single ring of hairs | 10 |
10 | Corolla ribbed inside; apices of corona lobes sagittate | D. rimicola |
– | Corolla smooth inside; apices of corona lobes cuneiform | D. tomentella |
11 | Staminal corona lobes reduced to minute swellings | D. kerrii |
– | Staminal corona lobes stalked and anchor-shaped or sagittate | 12 |
12 | Branches and leaves succulent | 13 |
– | Branches and leaves not succulent | 14 |
13 | Apices of staminal corona lobes obtuse | D. phuphanensis |
– | Apices of staminal corona lobes retuse | D. tonkinensis |
14 | Corolla tube and lobes glabrous inside | D. calva |
– | Corolla with hairs at mouth of tube or on adaxial side of lobes | 15 |
15 | Corolla with two distinct rings of hairs only in mouth of tube | D. fruticulosa |
– | Corolla with a single ring of hairs around mouth of tube | 16 |
16 | Corolla lobes adaxially pubescent | 17 |
– | Corolla lobes adaxially glabrous | 19 |
17 | Corolla lobes triangular, with a ring of hairs around base only | D. albida |
– | Corolla lobes lanceolate, with hairs from base to the middle | 18 |
18 | Leaves 1.5–3.0 × 0.7–1.3 cm; corona lobes anchor-shaped with rounded apices | D. tricholoba |
– | Leaves 2.5–6.5 × 0.9–2.5 cm; corona lobes sagittate with obtuse or truncate apices | D. singularis |
19 | Corolla greenish-white with purple lines alternating with lobes, mouth of corolla tube hairy throughout | D. punctate |
– | Corolla white or creamy white, with a ring of hairs in mouth of tube | D. acutifolia |
The authors thank the herbaria BK, BKF and K for providing information on the type specimens for this study. We thank the officers in Phu Pha Yon National Park for help while collecting plant specimens on field trips. Thanks for linguistic advice from Dr. Adrian Roderick Plant, Mahasarakham University. Thanks for valuable comments and suggestions from the editor and reviewers. This research project was financially supported by Mahasarakham University (Fast Track 2020).