A new species of Dischidia (Apocynaceae, Asclepiadoideae) from North-eastern Thailand Author Promprom, Wilawan Author Chatan, Wannachai text PhytoKeys 2020 144 23 30 http://dx.doi.org/10.3897/phytokeys.144.47977 journal article http://dx.doi.org/10.3897/phytokeys.144.47977 1314-2003-144-23 0D98F6DD8B6A5EF792509C549B4EC0EE Dischidia phuphanensis Chatan & Promprom sp. nov. Figures 1 , 2 Diagnosis. 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 1 , 2 ) Figure 1. Dischidia phuphanensis . A Plant climbing on rock B plant climbing on branches of shrub 2-3 m tall C branches and leaves D inflorescence E follicle (nearly mature) F dehiscent follicle. Photographed by Wannachai Chatan from W. Chatan 2489 ( A-D ) and W. Chatan 2904 ( E, F ). Figure 2. 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 . Type. 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!). Description. 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 x 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 x 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 x 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 x 1.0-1.8 mm; pedicels 1-2 x +/- 0.5 mm. Sepals greenish-white, lobes ovate, 0.6-0.8 x 0.5-0.8 mm, apex round, without colleters. Corolla broadly urceolate or slightly globose, 2.4-2.6 x 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 x 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 x 0.8 mm, apex obtuse. Pollinarium erect, ca. 2 mm long. Pollinium yellow, 0.6-0.8 x 0.20-0.22 mm, ellipsoidal; translator arms 1.0-1.2 mm long; corpusculum ovate, reddish-brown, 0.15-0.16 x 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 x 2.5-3.0 mm, green when immature changing to brown when ripe. Seed slightly cylindrical, 3.8-4.0 x 1.3-1.5 mm, base obconic, bearing white coma 30-32 mm long. Additional specimen examined. 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). Phenology. Flowering in July-September and fruiting in Aug-December. Distribution. The new species is endemic to Thailand and is known only from the type locality, Phu Pha Yol National Park, Sakon Nakhon Province, north-eastern Thailand (Figure 3 ). Figure 3. Distribution of Dischidia phuphanensis (black triangle) in Phu Pha Yol National Park, Sakon Nakhon Province, Thailand. Ecology. This new species grows in both slightly open and in shaded areas in mixed deciduous forest at an elevation of 300-400 m. Vernacular name. Thao Rag Noi. Etymology. The specific epithet of Dischidia phuphanensis refers to its type locality, the Phuphan mountain range. Preliminary conservation status. 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 ( IUCN 2017 ). Discussion. Dischidia phuphanensis is similar to D. tonkinensis , from China, Indochina and Thailand ( Thaithong et al. 2018 ). Similarities include their stems (thick, succulent, 2-3 mm in diameter, glabrous), glabrous petiole and lamina, succulent and coriaceous leaves and their glabrous corolla lobes. However, the new species differs from D. tonkinensis in its elliptic or narrowly elliptic or slightly oblanceolate leaves, the obtuse apex of the staminal corona lobes, the yellow base of the corolla tube, the light yellow or white apices of the lobes and absence of a corolline corona. Dischidia tonkinensis has ovate to ovate-elliptic, or rarely obovate lamina, the apices of the staminal corona lobes are retuse; it has a white or orange-yellow corolla tube and lobes and possesses a corolline corona. The new species is similar to D. acuminata Costantin, from Vietnam, in that they share the 1-5 branches to the inflorescence, the short peduncle 0-3 mm long and the absence of a corolline corona. It differs from D. acuminata by the triangular to deltate corolla lobes and with acute apices (narrowly shape, thick and abaxial side nose-like in D. acuminata ( Constantin 1912 )) 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 Thaithong et al. (2018) and nineteen species were recognised. This was made up of one species with pitcher-like leaves and 18 species with non-pitcher-like leaves. After this new species is added to this group, the number of species with non-pitcher-like leaves is 19. A key to the species with non-pitcher-like leaves in Thailand is provided below and is modified from Thaithong et al. (2018) . Details of the morphological differences between D. phuphanensis and D. tonkinensis are presented in Table 1 . Table 1. 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
Key to species of Dischidia with non-pitcher-like leaves in Thailand
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 x 0.7-1.3 cm; corona lobes anchor-shaped with rounded apices D. tricholoba
- Leaves 2.5-6.5 x 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