Staurogyne Wall. is a pantropical genus of Acanthaceae which has been recently revised for the Americas by Braz & Monteiro (2017), who recognised 28 species, and for Africa by Champluvier (1991), who recognised nine species. The majority of species (±100), however, are recorded from Asia where there has been no comprehensive study of the genus apart from Bremekamp’s (1955) revision of the Malaysian species. Many of the Asian species are poorly known, often from the type alone and, in the absence of a modern revision, it must be assumed that more species await discovery, while a degree of synonymy will become apparent. In the case of Myanmar nine species were listed by Kress et al. (2003) but recent field work in Sagaing Region has resulted in the discovery of two new species, S. yamokmehong J.R.I.Wood & K.Armstr. and S. filisepala J.R.I.Wood & K.Armstr., both described below.

Staurogyne species are erect or creeping herbs, subshrubs or shrubs, the calyx 5-lobed, the sepals unequal to subequal, with an androecium of four didynamous stamens with bithecous anthers. The genus belongs to the subfamily Nelsonioideae Pfeiff. characterised by descending-cochlear corolla aestivation, loculicidal capsules without retinacula, the absence of cystoliths on the leaves, as well as numerous ovules varying in number from six to many (Scotland & Vollesen 2000; Manzitto-Tripp et al. 2022).

Materials & Methods

This paper is based in the first place on fieldwork in Myanmar carried out by Kate Armstrong, Thet Yu Nwe and colleagues with information on medicinal and other uses provided by local informants from the Shan Ni community of Nam Sa Bi village adjacent to Htamanthi Wildlife Sanctuary of Sagaing Region, Myanmar. Species delimitation was made by consulting relevant literature, particularly Clarke (1884) and Hossain (1972) and, especially, by study of type and other collections at E and K.

Taxonomic Treatment

Staurogyne yamokmehong J.R.I.Wood & K.Armstr., sp. nov. Type: Myanmar, Sagaing Region, Hkamti Distr., Homalin township, Htamanthi Wildlife Sanctuary, Nam Phi Lin Stream, Camp 1; 25°41'35.9"N 95°30'59.5"E, 167 m, 17 March 2019, Kate Armstrong, Thet Yu Nwe, Marshall Kramer, Wah Wah Linn, Myo Khaing, Thar Myint, Phoe La Pyae, Aung Kyi, Kyee Nyo, Han Sein Myint, Maung Nge, Myint Oo 4471 (holotype NY-04300123, isotypes CAS, E, FHO, RAF).

http://www.ipni.org/urn:lsid:ipni.org:names:77301113-1

Small, erect herb or subshrub, 20 – 35 (– 50) cm high, stem woody. Leaves c. 3 – 9, clustered on stem 3 – 10 cm above ground level, ± equal in each pair, shortly petiolate, lamina 3.5 – 20.5 × 1.8 – 6.5 cm, obovate to broadly oblong-obovate, apex obtuse, margin obscurely crenate to subentire, narrowed basally to a narrow, rounded base, adaxially dark green, glabrous or with scattered hair bases, veins prominent, 8 – 10 pairs; abaxially whitish-green with prominent red-brown venation, brownish crisped-pubescent especially on the veins; petiole 1.4 – 2.5 cm, crisped-pubescent. Inflorescence a terminal thyrse, 8 – 25 (– 42) cm long and 7 – 15 mm wide; rhachis glandular-pilose up to 42 cm long; branches up to 10, arising irregularly from main axis, usually simple, occasionally with 2 lateral branches, 2 – 9 cm long; flowers solitary, arising along the branches, up to 8 mm apart below, reducing to c. 3 mm apart near tips; bracts at base of main branches often caducous and 1-veined, subulate, 2 – 2.5 mm long, thinly pubescent; pedicels solitary, 0.5 – 1.5 mm, pubescent; bracteoles at base of pedicels similar to bracts but shorter, c. 1 mm long; calyx 5-lobed to near base, lobes narrowly linear, acute, mucronulate, c. 2.5 mm long at anthesis, accrescent to 5 mm, 0.5 – 1 mm wide, 1-veined, sparsely pubescent with short septate hairs, minutely white-ciliolate on margins, pink when young, the outer 2 slightly broader than inner 3; corolla 7 – 9 mm long, campanulate above a short basal tube c. 1.5 – 2 mm long, obscurely bilabiate, the lobes ovate c. 1.5 × 1.5 mm, obtuse, white except for dull violet colouring around throat at base of lobes, thinly pubescent with spreading hairs; stamens 4, didynamous, inserted just above basal cylindrical part, filaments c. 4 mm long, thinly pilose with septate hairs, anthers ellipsoid, 0.75 × 0.5 mm, basally acute, shortly exserted; style 8 mm long, glabrous or with a few short hairs; stigma shortly bifid, weakly exserted; ovary 1 × 0.5 mm, glabrous, oblong, narrowed slightly at both ends. Capsule oblong in outline, glabrous, 3.5 × 1.5 mm; seeds numerous, ovoid, glabrous, brown, c. 0.2 × 0.1 mm. Figs 1, 2.

Fig. 1
figure 1

Staurogyne yamokmehong. A habit; B adaxial leaf surface; C abaxial leaf surface; D indumentum of inflorescence rhachis; E flower; F calyx, ovary and style; G corolla opened up to show stamens with (right) ovary and style; H fruiting calyx and capsule; J section of capsule opened to show seeds; K seed. A – H from Phoe la Pyae 203, J – K from Armstrong et al. 4471. drawn by rosemary wise.

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Fig. 2
figure 2

Staurogyne yamokmehong. A branch of inflorescence showing calyx and capsule apex; B flowers; C inflorescence D leaf adaxial surface (above), abaxial surface (below); E habit. Scale bars A = 3.5 mm, B = 8 mm, C = 1.5 cm, D = 2.5 cm, E = 2 cm. From Armstrong et al. 4471. photo montage by charlotte holden.

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recognition. The new species belongs to subgen. Staurogyne, sect. Staurogyne, subsect. Macrosepalae Bremek. according to the revision of the Nelsonieae by Bremekamp (1955) which was followed by Hossain (1972). It resembles Staurogyne gracilis (T.Anderson) Kuntze but differs in the smaller, distinctly petioled leaves with prominent, abaxially crisped-pubescent veins (leaves sessile, the veins neither prominent nor pubescent), larger calyx (2.5 – 5 mm vs 1.5 – 2.5 mm) and shorter, distinctly bell-shaped corolla (Fig. 2B) with subcylindrical base, 8 – 9 mm long, (vs corolla 12 – 13 mm, gradually widened from base). The smaller leaves and less densely hairy inflorescence axes may or may not be significant. Staurogyne yamokmehong also resembles S. paniculata (Wall.) Kuntze but the leaves are oblong-obovate, narrowed to a rounded base and clustered towards the base of the stem with internodes < 2 cm long (vs oblong, attenuate at base, dispersed along stem with internodes up to 4.5 cm long), bracteoles < 2.5 mm long (not up to 4.5 mm long), sepals narrowly linear-oblong, acute, straight, 5 mm long even in fruit (vs filiform, attenuate from base, often twisted, 6 – 7 mm long), corolla 7 – 9 mm long with the stigma very shortly exserted (vs 9 – 10 mm long, with the stigma exserted up to 3 mm).

distribution. Endemic to Sagaing Region in Myanmar and apparently restricted to Hkamti District. Map 1.

Map 1
figure 3

Map of Htamanthi Wildlife Sanctuary area, Sagaing, northern Myanmar showing distribution of Staurogyne yamokmehong (black circles) and Staurogyne filisepala (white diamond).

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specimens examined. myanmar. Sagaing Region: [Hkamti Distr., Homalin township, Htamanthi Wildlife Sanctuary] Upper Chindwin, Nampakom drainage, 1000 ft, 27 March 1927, C. E. Parkinson 5783 (K); ibid., Htamanthi Wildlife Sanctuary, behind Sun Bear Camp. Nam Eizu stream area, 25°30'51.7"N 95°31'29.7"E, 173 m, 23 March 2017, K. Armstrong et al. 2483 (CAS, E, FHO, NY-02655245, RAF); ibid., Htamanthi Wildlife Sanctuary, Nam Pa Gaon stream, behind Camp 2, 25°18'53.3"N 95°31'33.2"E, 196 m, 22 March 2018, K. Armstrong et al. 3455 (CAS, E, FHO, NY, RAF); ibid., Nat Inn Taung forest, 25°21'9.9"N 95°20'1"E, 200 m, 25 Feb. 2019, Phoe La Pyae 203 (CAS, FHO, NY, RAF); Layshi township, Myauk Khaw Lay Taung trail, 4 road miles E of Layshi, c. 0.3 map miles W off main road, east side of Paya Taung mountain towards summit, 25°27'14.1"N 94°59'12"E, 1362 m, 26 Nov. 2017, K. Armstrong et al. 3277 (CAS, E, FHO, NY-02655837, RAF).

habitat. Primary, selectively logged forest at 165 – 1365 m. Staurogyne yamokmehong is relatively common in the Kachin-Sagaing low elevation evergreen subtropical rainforest ecosystem (Armstrong et al. 2020; Murray et al. 2020a, b), which is a lowland (c. 100 – 300 m) evergreen closed forest ecosystem of northern Myanmar, where there is abundant rainfall (>2,000 mm annually) and generally moist conditions. It has also been reported from higher elevations in the Sagaing Warm Temperate Forest ecosystem of the Naga Hills (Murray et al. 2020a, b), although it is apparently less frequent there.

proposed iucn conservation status. Using Geocat (Bachman et al. 2011) this species has an area of occupancy of 16.000 km2 and extent of occurrence 637.651 km2, both resulting in a conservation assessment of Near Threatened (NT) following IUCN Standards and Petitions Committee (2019). However, is a relatively common plant in forest and the populations are not fragmented or in obvious decline so the assessment as Near Threatened (NT) might be premature, and a provisional assessment as Vulnerable (VU) might alternatively be made.

etymology. The specific epithet yamokmehong is derived from the Shan Ni name "yaa mok me hong" (), meaning medicine preventing the flower from falling, the name used by medical practitioners in the Hkamti District.

note. This species was first collected by the Scottish forester Charles Parkinson in 1927. The collection was incorporated in the Kew Herbarium and the sheet was annotated by Enayat Hossain saying it was a putative new species. The second and third authors (T.Y.N & K.E.A) and colleagues have recently made several additional collections from the same general area confirming the characteristics of this species.

observations. Since 2014, the New York Botanical Garden has been involved in an initiative to document the flora of Myanmar's Northern Forest Complex through botanical inventories in Kachin State and in and around Htamanthi Wildlife Sanctuary and the surrounding Naga Hills in Sagaing Region. As part of this project, information about traditional uses of plants has been carefully collected. Wide medical uses were recorded for the new species. These include a role as a hormone regulator as it is reportedly used for contraception and menstrual disorders; it is also reported to be a useful medicine for children whose hair has turned blond due to malnutrition, as well as for inflammatory gastrointestinal disorders. As well as its Shan Ni name noted above, it is also known as (“pwin-ma-cwe-s'e” meaning ‘flower not easily falling medicine’) by Burmese speakers.

Staurogyne filisepala J.R.I.Wood & K.Armstr., sp. nov. Type: Myanmar, Sagaing Region, Hkamti Distr., Homalin township, Nam Sa Bi village management area, 25°19'3.4"N 95°21'50.3"E, 247 m, 5 April 2017, Kate Armstrong, Thet Yu Nwe, Yunn Mi Mi Kyaw, Myo Khaing, Phoe La Pyae, Than Tun Oo, Lin Zaw, Aung Kyi 2660 (holotype NY-02655166).

http://www.ipni.org/urn:lsid:ipni.org:names:77301114-1

Erect herb or subshrub to 80 cm; stem woody, wrinkled when dry, densely strigose with matted tan-coloured hairs, glabrescent below. Leaves 6 – 7, regularly spaced on stem, ± equal in each pair, shortly petiolate, 18 – 24 × 4 – 5 cm when mature, oblong to oblong-oblanceolate, apex acute to shortly acuminate, margin obscurely undulate to entire, base cuneate, discolorous, adaxially dark green, glabrous, veins c. 20 – 25 pairs, abaxially whitish with scattered minute yellow hairs, glabrescent, midvein brown, veins strigose, the hairs tan or whitish; petiole 1.5 – 2 cm, strigose. Inflorescence formed of slender, simple, axillary racemes, 9.5 – 16.5 cm long, the lower 5 – 8.5 cm, flowerless, rhachis strigose, with white septate hairs, bracts at base of rhachis, oblong-lanceolate, 4 – 12 × 1 – 2 mm; indumentum as for leaves; flowers solitary, alternate along the rhachis, 4 – 8 mm apart, pedicellate; pedicels 3.5 – 5 mm long, strigose with white glandular and eglandular hairs mixed; bracteoles 2 – 3, 2.5 – 5 × 0.2 – 0.5 mm linear, sparsely strigose; calyx subequally 5-lobed to base; lobes filiform, becoming recurved and flexuous, 7.5 – 9 × 2 mm at base, narrowed upwards to < 0.5 mm, setose with white glandular and eglandular hairs mixed. Corollas not seen. Capsule oblong in outline, glabrous, c. 5.75 × 2 mm; seeds numerous, c. 28, subglobose, glabrous, c. 0.4 × 0.4 mm, obscurely pitted. Fig. 3.

Fig. 3
figure 4

Staurogyne filisepala. Photograph of holotype, Armstrong et al. 2660.

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recognition. This species also belongs to subgen. Staurogyne, sect. Staurogyne, subsect. Macrosepalae Bremek. according to the revision of the Nelsonieae by Bremekamp (1955) which was followed by Hossain (1972). It is distinctive because of its erect stem with regularly spaced leaves. The inflorescence is formed of long, simple axillary racemes with filiform calyx lobes and small linear bracteoles. All these suggest an affinity with Staurogyne lasiobotrys (Nees) Kuntze, a species from southern Myanmar, but the leaves are much longer (18 – 24 cm vs <11 cm), the calyx lobes are longer 7.5 – 9 mm (vs 6 – 7 mm) and their indumentum is relatively short compared to the long glandular pilose hairs of S. lasiobotrys. The filiform sepals suggest an affinity with S. simonsii (T.Anderson) Kuntze from the Khasi Hills in India but that species has a densely hirsute, very compact inflorescence with short dense racemes to c. 6 cm, and smaller leaves. S. shanica W.W.Sm. might be related because of the somewhat similar sepals but the only collection, the type, is very poor, essentially stemless, the inflorescence short with ovate bracteoles and leaves only up to 7 cm long. The leaf shape (but not their size) and the filiform calyx lobes resemble those of S. argentea Wall. but the dense subcapitate inflorescence and compact habit of that species are completely different.

distribution. Only known from the type collection. Map 1.

habitat. Primary, selectively logged forest at 247 m in the Kachin-Sagaing low elevation evergreen subtropical rainforest ecosystem (Armstrong et al. 2020; Murray et al. 2020a, b).

conservaton status. As this species is only known from a single collection with no details of its frequency, it can only be treated as Data Deficient (DD) according to IUCN Standards and Petitions Committee (2019).

etymology. The specific epithet filisepala refers to the narrow filiform calyx lobes.

notes. This species is only known from a single collection that lacks corollas. Nonetheless the relatively long flexuose calyx lobes (Fig. 3) are very distinct, especially when combined with the long racemes and the large oblong-oblanceolate leaves which are regularly spaced along the stem.

We recognise that it is unusual to publish a new species when reproductive structures on the specimen are partially lacking, although this is occasionally advisable to advance our understanding of a flora. We argue that it is justified in this case due to the morphological distinctiveness of the species and the importance of thoroughly documenting the flora of this poorly known region. The last author, KA, carried out botanical inventory work in the region from 2014 – 2019, making seven field trips to the area, and only collected this species on one occasion. Few, if any, other botanists have collected in and around Htamanthi Wildlife Sanctuary prior to this and few botanists have been there since. The current political situation in Myanmar makes it unlikely that botanical research will resume in the region for many years. In the meantime, we choose to document this species with the present material with the hope that future authors will be able to flesh out the description with details of the corolla and fruit characters.