Research Article |
Corresponding author: Sahut Chantanaorrapint ( sahut.c@psu.ac.th ) Academic editor: João Farminhão
© 2022 Amonrat Chantanaorrapint, Sahut Chantanaorrapint.
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:
Chantanaorrapint A, Chantanaorrapint S (2022) Aphyllorchis periactinantha (Orchidaceae, Neottieae), a new mycoheterotrophic species from peninsular Thailand. PhytoKeys 215: 107-115. https://doi.org/10.3897/phytokeys.215.91458
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A new orchid species from southern Thailand, Aphyllorchis periactinantha, is described and illustrated. The novelty is characterized by the subactinomophic flowers, the concave labellum, not divided into hypochile and epichile, the reduced staminodes, the shallowly bilobed stigma and the semicircular rostellum. A key to the species of Aphyllorchis in Thailand is updated.
achlorophyllous orchid, dipterocarp forest, Epidendroideae, peloric flower, Thai-Malay Peninsula, Ton Nga Chang Wildlife Sanctuary
Aphyllorchis Blume is one of the largest mycoheterotrophic orchid genera with 19 currently accepted species (
In November 2015, during an orchid survey in Ton Nga Chang Wildlife Sanctuary (TNCWS), Songkhla province, southern Thailand, an immature inflorescence of an unknown achlorophyllous orchid was observed. However, due to the immature flowers, it could not be accurately determined. Later, four further botanical surveys to TNCWS and Ban Yang Ko community forest resulted in four more collections of this unknown orchid. After careful examination, these specimens were identified as belonging to Aphyllorchis, however, they differed from all the other known species of the genus in Thailand. These specimens resemble A. anomala Dockr. from Australia, A. montana var. rotundatipetala (C.S.Leou, S.K.Yu & C.T.Lee) T.P.Lin from Taiwan, A. simplex Tang & F.T.Wang from China and Vietnam, and A. striata (Ridl.) Schltr. from Peninsular Malaysia and Borneo in having subactinomophic (peloric) flowers and a labellum not divided into hypochile and epichile as in most species of Aphyllorchis. Following a detailed comparison with closely related taxa, we here describe and illustrate these specimens as a new species.
Field surveys were carried out in TNCW and Ban Yang Ko community forest, Songkhla province, southern Thailand (Fig.
Similar to A. anomala, but differs in having a concave labellum without purple veins, acute at the apex, and a semicircular rostellum.
Thailand. Songkhla Province: Ton Nga Chang wildlife sanctuary, ca. 100 m, 06°59'43.91"N, 100°09'00.57"E, 26 December 2020, S. Chantanaorrapint & A. Chantanaorrapint 3109 (holotype: BKF!; isotype: PSU! [PSU00019495]).
Terrestrial, achlorophyllous herbs, with a suberect rhizome and an erect flowering shoot. Rhizomes pale brown, producing numerous horizontal roots; roots fleshy, 3.5–6.5 mm in diameter, pale brown, glabrous. Flowering shoots 70–150 cm tall, up to 9 mm in diameter at base, unbranched whitish or pale yellow, marked with purple stripes or spots, with 5–9 membranous sheaths at base and 10–15 scales above. Inflorescence racemose, terminal, 15–30 cm long, up to 32 flowers; rachis glabrous. Floral bracts reflexed, lanceolate to linear-lanceolate, acute to acuminate, 16.5–21.5 × 4.5–5.5 mm, whitish or pale yellow with purple stripes. Flowers opening widely, creamy white to pale yellow. Sepals creamy white to pale yellow, minutely tuberculate and sparsely pubescent on the adaxial surface, scattered with purple stripes or dots, concave, margins entire, apex acute; dorsal sepal narrowly ovate to lanceolate, 17.5–19.6 × 4.3–5.2 mm; lateral sepal obliquely narrow-ovate to obliquely lanceolate, 16.8–19.0 × 4.2–5.1 mm. Petals creamy white to pale yellow with purple veins, oblong-lanceolate, 16.0–16.5 × 3.9–4.3 mm, slightly falcate at apex, base obtuse to subtruncate, apex acute, margin entire or minutely erose and slightly recurved backward in the middle, keeled adaxially along midrib. Labellum creamy white to pale yellow, simple and not divided into hypochile and epichile, oblong-lanceolate, 16.2–17.0 × 3.8–4.5 mm, more or less folded along a midrib, concave at the basal part, apex acute, margin nearly entire or minutely erose, abaxial and adaxial surfaces nearly smooth. Column slender, subclavate, yellow at the apical third and purple at the proximal two thirds, gently curved throughout its entire length, 10–12 mm long, without column wing or a hook-shaped appendage on ventral side; clinandrium with a rather large central dome-like outgrowth; stigma more or less ovate in outline, shallowly bilobed at the lower margin; anther cap ovoid in outline, 2.0–2.2 mm long, apex obtuse; pollinia 2, soft and mealy, without caudicles. Pedicel with ovary slightly bent upwards or downwards, 18.5–23.5 mm long, ca. 2 mm in diameter, dark purple, pubescent, bearing sparse glandular hairs. Capsules (immature) pendulous, claviform or fusiform, 5.5–6.5 cm long, 0.7–1.1 cm diameter. Seeds not seen.
Thailand. Songkla Province: Ton Nga Chang Wildlife Sanctuary, ca. 100 m, 06°59'43.91"N, 100°09'00.57"E, 22 October 2017, S. Chantanaorrapint & A. Chantanaorrapint 2810 (PSU), 16 November 2018, S. Chantanaorrapint & O. Suwanmala 2732 (PSU); Ban Yang Ko Community Forest, 7 December 2021, C. Leeratiwong 21-1752 (PSU).
Flowering and fruiting observed from October to December.
Aphyllorchis periactinantha is known only from two localities in Songkhla province (Fig.
Aphyllorchis periactinantha A.Chantanaorr. & Chantanaorr. A flower, lateral view B flower, top view C floral bract D column and labellum, side view E dorsal sepal F, G lateral sepals H, I petals J labellum K column and anther cap in ventral view L, M anther caps. Drawn by S. Chantanaorrapint.
Aphyllorchis periactinantha A.Chantanaorr. & Chantanaorr. in situ A habit B inflorescence C flower in front view D flower in oblique view with stingless bee (Tetragonula sp.) E column in ventral view F immature fruits G rhizome and roots A–E, G photographed by S. Chantanaorrapint F by C. Leeratiwong.
Greek prefix peri-, about, actis, ray or radiate, and anthos, flower, alluding to subactinomorphic flowers.
This species is currently known from two subpopulations, representing two locations, which are in protected areas (Wildlife Sanctuary and community forest). One of the subpopulations is located beside a waterfall, which is a common visiting site for tourists. Therefore, habitat quality is threatened by trampling and other destructive activities potentially caused by regular visits by tourists to the area, namely the attraction of wild boars. Together, these have the potential to cause a population reduction. The other subpopulation is also somewhat disturbed by human activities such as illegal logging. Moreover, the number of mature individuals observed is fewer than 50. The extent of occurrence cannot be estimated because the species is known only from two subpopulations and its area of occupancy is estimated to be only 8 km2. Aphyllorchis periactinantha is, therefore, assigned a preliminary status of Critically Endangered based on subcriterion C2a(i).
Aphyllorchis periactinantha is morphologically similar to A. anomala, which is endemic to Queensland, Australia (
The new species can be confused with A. striata from Peninsular Malaysia and Borneo (
The new species also resembles A. montana var. rotundatipetala, endemic to Taiwan (
Morphological differences among Aphyllorchis periactinantha, A. anomala, A. montana var. rotundatipetala, A. simplex and A. striata. The characters of previously described species are taken from the protologues and from recent publications (
Characters | A. periactinantha | A. anomala | A. montana var. rotundatipetala | A. simplex | A. striata |
---|---|---|---|---|---|
dorsal sepal | narrowly ovate to lanceolate, 17.5–19.6 × 4.3–5.2 mm, apex acute | oblong-cuculate, ca. 12 × 3 mm, apex acuminate | oblong-cymbiform, 10–12 × 4.0–5.5 mm, apex obtuse | narrowly elliptic, 8–10 mm long, apex acute to obtuse | lanceolate, ca. 12–14 × 2.5–3.0 mm, apex acute |
petals | oblong-lanceolate, 16.0–16.5 × 3.9–4.3 mm, apex acute | oblong, ca. 12 × 2 mm, apex acuminate | oblong, 9.5–11.5 × 3.5–4.0 mm, apex rotundate or obtuse | narrowly elliptic, 8–10 mm long, apex acute to obtuse | lanceolate, ca. 11–14 × 2.0–2.5 mm, apex acute |
labellum | oblong-lanceolate, 16.2–17.0 × 3.8–4.5 mm, folded along a midrib, concave at the basal part apex acute, lateral margins not decurved | oblong-acuminate, ca. 11 × 2.5 mm, flat entirely, apex acuminate and slightly twisted, lateral margins decurved | oblong, 9.5–11.5 × 3.5–4.0 mm, flat entirely, apex obtuse or rotundate, lateral margins recurved backward at middle | oblanceolate, 9–10 × 2–2.5 mm, flat entirely, apex acute and slightly decurved, lateral margins slightly decurved | 3-lobed with indistinct side lobes, ca. 11–14 × 2.5–3.0 mm, almost flat, apex acute, lateral margins rolled at the basal part |
staminode | reduced | reduced | Present | present | reduced |
rostellum | semicircular, entire apex | triangular, entire apex | ovate-lingulate, entire apex | ovate, emarginate apex | lingulate, entire apex |
One could argue that the new species could simply represent an abnormal (peloric) form of another Aphyllorchis species, such as A. maliauensis Suetsugu, Suleiman & Tsukaya from Borneo (
There are now five species of Aphyllorchis known from Thailand. An updated key to distinguish these species is given below.
1 | Flowers subactinomorphic; labellum somewhat similar to the sepals, undivided into hypochile and epichile | A. periactinantha |
– | Flowers zygomorphic; labellum distinctly different from the sepals, divided into hypochile and epichile | 2 |
2 | Sepals caudate, longer than 20 mm | 3 |
– | Sepals rounded to obtuse, shorter than 20 mm | 4 |
3 | Hypochile with well-developed side lobes; epichile densely papillose on adaxial surface; anther apex rounded to obtuse | A. caudata |
– | Hypochile with indistinct side lobes; epichile nearly glabrous on adaxial surface; anther apex forming a horn-like projection | A. evrardii |
4 | Sepals longer than 7 mm. Labellum longer than 6 mm; epichile ovate to slightly 3-lobed | A. montana |
– | Sepals shorter than 7 mm. Labellum shorter than 6 mm; epichile cordate | A. pallida |
We would like to thank O. Suwanmala for her assistance during fieldwork, C. Leeratiwong for providing his collection and photograph, and the curator and staff of SING for allowing us to access the available specimens. We would also like to thank J. Farminhão and the anonymous reviewers for their valuable comments and suggestions to improve the manuscript. This work was supported by the Prince of Songkla University annual government expenditure under the Plant Genetic Conservation Project Year 2021 under the Royal initiative of Her Royal Highness Princess Maha Chakri Sirindhorn.