Geostachys aristata Škorničk., Q.B.Nguyen & H.Đ.Tr

Leong-Škorničková, Jana, Bình, Nguyén Qu ốc, Đăng, Tr ần H ữu, Trư ờng, Lưu H ồng & Nuraliev, Maxim S., 2023, A revision of Geostachys (Zingiberaceae: Alpinioideae) in Cambodia, Laos and Vietnam, including a new species, G. aristata, Phytotaxa 585 (4), pp. 245-260 : 250-254

Geostachys aristata Škorničk., Q.B.Nguyen & H.Đ.Tr ẫn, sp. nov. ( Fig. 1 , 3 , 4 )

Diagnosis: —Similar to G. annamensis in the overall habit and erect inflorescences composed of 2–3-flowered cincinni of white flowers with labellum and stamen spotted with dark pink to red, but differs from the latter species by the green leaf sheaths and ligules (vs leaf sheaths with dark red reticulation and dark red ligules), most often longer petioles (5–30 mm vs 1–7 mm long), bracts and bracteoles greenish (vs white tinged pink) with prominently aristate (vs round) apices, calyx lobes prominently mucronate with mucros 2–5 mm long (vs calyx lobes blunt, with apices less than 1 mm long), labellum with crimson spots extending to the margin (vs with crimson spots and lines limited to the centre), and longer anther crest (5–6 mm vs 2–3 mm long).

Type: — VIETNAM. Kon Tum province: Kon Plông district, Xã Hiḗu commune, 14°38’58.3”N 108°24’57.3”E, 1209 m, 24 April 2012, J. Leong-Škorničková, Q.B. Nguyễn, H.Đ. Trǻn & E. Záveská JLS-1561 (holotype SING: SING0197751 ! [including flowers preserved in spirit]; isotypes E [mounted over two sheets E00666509 ! & E00666510 !], P [mounted over two sheets P00840190 ! & P00840191 !], PR!, VNMN! [including flowers preserved in spirit]) .

Clump-forming herb up to 2 m tall. Rhizome supported up to 40 cm above the ground by stilt roots, sheathed by dry brown scales, internally cream white. Leafy shoots with 7–12 leaves per pseudostem, bladeless at basal 1/3; bladeless sheaths 4–6, most basal (outermost) sheaths very short, dry and brown, inner sheaths distally gradually longer, green, abaxially pubescent, with a prominent hyaline margin (more prominent in dry material); leaf sheaths green, pubescent abaxially along the centre, glabrescent towards margin, margin hyaline (more prominent in dry material), basally glabrous or nearly so, distally pubescent; ligule 2–6 mm long, apex round (rarely obscurely bilobed), green, glabrous at base, pubescent at margin (glabrescent with age); petiole ca. 5–30 mm long, shallowly canaliculate, green, adaxially more or less glabrous, abaxially pubescent; leaf blade ovate to elliptic, 23–47 cm long, 8–9 cm wide, adaxially green, sparsely hirsute, abaxially paler green, more densely hirsute, base obtuse to round, apex prominently acuminate, midrib adaxially sunken, pale green to green, mostly glabrous, abaxially protruding, pale green, densely hirsute. Inflorescence radical, erect; peduncle ca. 15 cm long, covered by 8–13 sheathing bracts; sheathing bracts distichous, broadly to narrowly ovate, overlapping, basal ones shorter, tightly appressed to the peduncle, distal 5–6 significantly larger and puffed, basal ones soon becoming brown and papery, distal ones green, adaxially glabrous, abaxially shortly pubescent, glabrescent on sides, margin hyaline (more prominent in dry material); thyrse dense, many-flowered; rachis 7–10 cm long, bright green, glabrous to sparsely hirsute, shortly branched; bracts elliptic, slightly ovate or slightly obovate, 20–40 mm long (excluding the mucro), 8–18 mm wide, aristate to mucronate (mucro 3–7 mm long), semi-translucent pale green, glabrous, each subtending cincinnus of 2–3 flowers on 2–5 mm long branch; branches evenly distributed around rachis, of the same colour and indumentum as rachis; bracteoles elliptic, slightly ovate or slightly obovate, 10–20 mm long (excluding the mucro), 5–15 mm wide, aristate to mucronate (mucro 1–4 mm long), semi-translucent pale green, glabrous. Flower ca. 6 cm long, gullet-type; pedicel 1–2 mm long, green, glabrous; calyx tubular, ca. 22 mm long, with a dorsal unilateral incision ca. 10–11 mm from apex, apex 3-lobed, lobes prominently mucronate (mucro 2–5 mm long), semi-translucent pale green (slightly darker at mucro), glabrous; floral tube ca. 23 mm long, externally white and glabrous, internally white at base, pale pink distally, with glandular hair; dorsal corolla lobe ovate with prominently sharply mucronate apex, ca. 32 mm long (including ca. 7 mm long mucro), ca. 19 mm wide, white, glabrous; lateral corolla lobes ovate with obtuse apex, ca. 23 mm long, ca. 19 mm wide, white, glabrous; labellum obovate, 35–40 mm long, 30–40 mm wide (50–60 mm if inclusive of staminodes), apex bilobed with incision 5–7 mm long, white with narrow white median, tinged pink at the sides of median fading white towards the margins, covered (except the median) with mixture of dark pink to red spots and larger blotches extending all the way towards the margins, adaxially with white glandular hair in the centre, abaxially glabrous; lateral staminodes irregularly obovate, ca. 25 mm long, ca. 20 mm wide, connate to labellum in basal 2/3, white with a mixture of dark pink to red small spots and larger blotches extending all the way towards the margins; stamen 20–22 mm long (including crest); filament 6–7 mm long, ca. 3 mm wide, dorso-ventrally compressed, tinged pink to red, with red spots distally, mostly glabrous with occasional short glandular hair; anther 13–15 mm long (including crest); connective pale yellow with red spots, mostly glabrous with occasional short glandular hair dorsally; crest 5–6 mm long, semi-circular, crenulate, white with deep pink to red spots, glabrous; anther thecae 7 mm long, dehiscing through the entire length; ovary trilocular with central placentation, ellipsoid, 5–5.5 mm long, 3–4 mm in diam., pale green, glabrous; epigynous glands two, ca. 2.5 mm long, 1–1.5 mm in diam., enveloping the base of style, ochraceous; style white, turning pink near stigma, glabrous; stigma capitulate, deep pink to red; ostiole transverse, forward-facing, ciliate. Fruit subglobose to oblate hesperidium with three shallow longitudinal grooves, 15–20 mm in diam., bright green, glabrous, with persistent calyx; seeds 3.5–5 mm long, 2.5–4 mm in diam. (measurements include aril), dark brown, each fully enclosed in semi-translucent white juicy aril.

Etymology:— The specific epithet of G. aristata refers to the prominently aristate to mucronate apices of bracts, bracteoles and calyx lobes which readily distinguish the new species from the morphologically closest G. annamensis .

Distribution & IUCN preliminary assessment:— Endemic to central Vietnam. This species is known from one historical and three recent collections spanning over three provinces (Ðà Nẵng, Kon Tum and Quảng Nam).

The EOO is estimated at 4603 km 2, AOO is estimated at 16 km 2. The forested area in Kon Tum province, Kon Plông district (the type location) is not under any legal protection, and the type population, which has less than 10 observed adult individuals, is small enough to be affected by stochastic events such as a tree falls. Similar situation has been observed at both locations in Quảng Nam province , Tây Giang district , with none of the locations legally protected and occurrence of adult individuals being rare and sporadic. No information is available about populations at Bà Nà hills (Ðà N ẵng province). Although with the existence of suitable habitats in adjacent areas this species possibly inhabits adjacent locations, the vast majority of Geostachys species are considered hyper-endemic to their respective type localities ( Lau et al. 2007) and therefore the total distribution area of each species is not expected to be large. Moreover, since the forests inhabited by the three recently known populations (one in Kon Plông and two in Tây Giang) are not within any protected areas (such as National Park or Nature Reserve), they are known to suffer from clearing for the agricultural use of the land. We therefore propose to treat this species provisionally under the category of Endangered (EN) (B1, B2a,b(iii)).

Ecology & phenology:— Growing on slopes in slightly disturbed montane evergreen broadleaved primary forest, at elevations of 800–1500 m a.s.l. Flowering of the population in Kon Tum province was observed in April and is likely to continue into May. The fruiting of the populations in Quảng Nam province was observed in August and October, while the fruiting specimen from Bà Nà hills (Ðà Nẵng province) is dated from July.

Additional specimens examined (paratypes):— VIETNAM. Ðà Nẵng province-level municipality: Annam, Bana près Tourane [Mount Bà Nà], 1500 m, 17 July 1923, E. Poilane 7227 ( P: P02203166 , fruiting) ; Qu ảng Nam province: Tây Giang district, A Xan commune, 15°48’34”N 107°18’43”E, 1155 m, 26 October 2017, H.Đ. Trǻn & H.C. Nguyễn TG639 ( SGN, fruiting); Tây Giang district, Tr’Hy commune, 15.84449°N 107.41179°E, 816 m, 10 August 2018, M.T. Đặng TG1061 ( SGN, fruiting) .

Notes: —This species is readily recognisable in the field by its very showy dense inflorescences. The semitranslucent greenish somewhat crenate bracts and bracteoles with aristate or mucronate apices give it almost ‘fluffy’ appearance. It is unfortunate that this beautiful species is unlikely to do well in cultivation (based on the general knowledge about the genus: Leong-Škorničková & Newman 2015), as most of the stilt-rooted ginger species require conditions of fairly undisturbed primary forest to grow well. While the colour differences of the pseudostem and ligules outlined in the diagnosis are helpful only in identification of living material, the difference in morphology of bracts, bracteoles and calyces, as well as prominent hyaline margins on leaf sheaths and sheathing bracts, and wider leaf blades, makes this species easy to recognise even in dry herbarium material.

Although G. aristata is morphologically most similar to G. annamensis , it is also similar to two Thai species, G. smitinandii K. Larsen (2001: 17) and G. tratensis Picheansoonthon & Mayoe (2011: 133) , and three species from Peninsular Malaysia, G. leucantha B.C. Stone (1980: 77) , G. megaphylla Holttum (1950: 228) and G. montana ( Ridley 1909: 78) Holttum (1950: 229) . All these species share characters of erect inflorescences with flowers evenly arranged around the rachis, and flowers predominantly coloured white with some pink spotting and/or lines. The aristate apices of bracts and bracteoles, as well as mucronate calyx lobes distinguish G. aristata from all of these species.

Figures

FIGURE 1. Distribution map of Geostachys species in Cambodia, Laos and Vietnam.

FIGURE 3. Geostachys aristata. A. Habit. B. Inflorescences (side view). C. Rhizome with stilt roots and inflorescences. D. Inflorescences (top view). E. Detail of leaf sheaths and ligules. All from the type Leong-Škorničková et al. JLS-1561. Photo by J. Leong-Škorničková.

FIGURE 4. Geostachys aristata. A. Flower (side view). B. Flower (front view). C. Flower dissection, from left: Flower, bract, bracteole, calyx, floral tube with stamen attached, labellum with lateral staminodes attached and three corolla lobes above it. D. Stamen from adaxial, abaxial and side view, and ovary with epigynous glands. E. Infructescence. F. Cross sections of fruit. G. Seeds enclosed in arils.A–D from the type Leong-Škorničková et al. JLS-1561; E, F from Trǻn & Nguyễn TG639; G from Đặng TG1061. Photo by J. Leong-Škorničková (A–D), H.Đ. Trẫn (E, F), M.T. Đặng (G).