Gastrodia maliauensis Suetsugu, M.Suleiman & Tsukaya, 2018

Suetsugu, Kenji, Suleiman, Monica & Tsukaya, Hirokazu, 2018, A new species of Gastrodia (Gastrodieae, Epidendroideae, Orchidaceae) from the Maliau Basin Conservation Area, Sabah, Borneo, Phytotaxa 367 (1), pp. 78-84 : 78-82

Gastrodia maliauensis Suetsugu, M.Suleiman & Tsukaya , sp. nov. ( Figs. 1–2 )

Type:— MALAYSIA. Sabah: Maliau Basin Conservation Area, from Ginseng Camp (N4°44’44”; E116°55’05”, 680 m alt.) to Maliau Falls (N4°46’06”, E116°55’05”, 440 m), 16 August 2017, Tsukaya, Suetsugu & Anthony TSA-5 (holotype: BORH; isotype: TNS, a flower in the spirit collection) .

Gastrodia maliauensis is similar to G. verrucosa Blume (1856: 175) in possessing bell-shaped flowers with verruculose outer surfaces, sepals connate ca. 2/3 of their length and petals connate ca. 2/3 of their length. However, it differs from G. verrucosa in lacking globose processes just below the stigma (vs. having these processes), stelidia with obtuse apices (vs. acute apices) and different ridges on the lip disc (two central ridges extending to apex and other ridges only extending to near the middle vs. all 6–8 ridges extending to apex).

Terrestrial, mycoheterotrophic herbs. Rhizome tuberous, fusiform or cylindrical, covered with numerous scales. Stem erect, dark brown, ca. 20 cm long, ca. 2.5 mm in diameter, nodes 10, with tubular, membranous scale leaves. Bracts ovate, up to 8 × 4 mm. Inflorescence racemose, rachis, ca. 3 cm long, densely 10 flowered. Pedicel and ovary up to 12 mm long. Flower, bell-shaped, slightly tilted upwards, resupinate, ca. 10 mm long, 6.4 mm in diameter. Sepals and petals united, forming a five-lobed perianth tube, outer surface pale greenish brown to dark brown, verruculose. Sepals subsimilar, ca. 10 mm long, adnate to petals for ca. 2/3 of their length; lateral ones connate ca. 2/3 of their length; inner surface of dorsal sepal ivory, smooth, margins entire; half of inner surface of lateral sepals in contact with dorsal sepal ivory, smooth, margins entire; half of inner surface of lateral sepals in contact with one another dark brown, smooth, margins entire; free portion of dorsal sepal straight, ovate-triangular, obtuse at apex, ca. 4.2 × 3.8 mm; free portions of lateral sepals, triangular, acute at apex, ca. 4 × 4 mm. Free portions of petals ovate or elliptic, ca. 1.8 × 2.2 mm, base contracted, margin slightly undulate. Lip adnate to column foot, dark brown, ca. 6.8 × 3.8 mm; hypochile with 2 elliptic calli; epichile ovate, base contracted, with 6–8 ridges on disc (two central ridges extending to apex and other ridges only extending to near the middle), margin slightly undulate, apex portion ligulate, ca. 1 mm wide. Column straight, semi-cylindrical, 6.1–6.3 × 1.9–2.0 mm, white; lateral wings (stelidia) distinct, narrow, edges parallel to column, base slightly angled, reddish orange, apex obtuse; rostellum prominent; stigma located at base. Anther hemispheric, ca. 1.2 mm in diameter, pollinia 2. Fruits and seeds not seen.

Distribution and phenology:— To date, we found only one flowering individual in the Maliau Basin Conservation Area, Sabah, Borneo , Malaysia. Its habitat is the wet understory of a forest dominated by Dipterocarpaceae species.

Preliminary IUCN conservation status:— Critically Endangered on the basis of one location, a single mature individual and a single population. [CR: D].

Taxonomic notes:— Gastrodia maliauensis is similar to G. verrucosa in possessing possessing bell-shaped flowers with verruculose outer surfaces, sepals connate ca. 2/3 of their length, and petals connate ca. 2/3 of their length. However, these characters are similar to those of other species that are morphologically similar to G. verrucosa ( Suddee & Harwood 2009) . This complex probably includes G. appendiculata Leou & Chung (1991: 138) , G. boninensis Tuyama (1939: 2) , G. confusa Honda & Tuyama (1939: 659) , G. confusoides Hsu, Chung & Kuo (2012: 273) , G. nantoensis Hsu & Kuo ex Lin in Lin et al. (2016: 99), G. sabahensis Wood & Lamb in Wood (2008: 139), G. shimizuana Tuyama (1982: 380) , and G. verrucosa . However, the taxonomic identity of G. verrucosa has remained somewhat problematic, mainly due to the incompleteness of the original description.

As stated by Ong (2015), the protologue of G. verrucosa by Blume (1856) is brief and vague: “flowers pedicellate, perigonium lobes subequal-obtuse, warty externally, column with two erect stelids” and cannot be used to identify specimens. Therefore, the descriptions and illustrations of G. verrucosa by Smith (1905, 1906, 1908) provide the only detailed information of the species based on specimens collected from Java, the type locality. Comparing our material to descriptions and illustrations of G. verrucosa by Smith revealed that G. maliauensis can be easily distinguished from G. verrucosa by analyzing column shape (without globose processes just below the stigma vs. with globose processes just below the stigma), stelidia (obtuse apex vs. acute apex), and pattern of ridges on the lip disc (only two central ridges extending to the apex and other ridges only extending to near the middle vs. all 6–8 ridges extending to the apex). In addition, G. maliauensis has a longer lip than G. verrucosa (> 6 mm vs. <5 mm; Smith 1905, 1906, 1908). Moreover, quantitative differences are also recognized. The stem of G. verrucosa was reported to be ca. 7 cm long and bears 2 flowers ( Smith 1905, 1906, 1908), while that in the new species is ca. 20 cm long and bears 10 flowers.

Seidenfaden & Wood (1992) noted that G. verrucosa occurs in Sumatra, Peninsular Malaysia, Java, and Japan by treating G. holttumii Carr (1929: 38) , G. confusa Honda & Tuyama (1939: 659) , and G. boninensis Tuyama (1939: 2) as synonyms of G. verrucosa and that the disjunct distribution pattern required further study. Suddee & Harwood (2009), who supported this view, also noted that the discovery of G. verrucosa in Thailand fills in part of the large distributional gap and that G. shimizuana Tuyama (1982: 380) is another synonym of G. verrucosa . However, owing to clear differences in lip and column morphology, which are key characters in Gastrodia taxonomy, we suggest that these species differ from both G. verrucosa and G. maliauensis . For example, the lips of both G. verrucosa and G. maliauensis bear 6–8 ridges that arise from the base of the epichile, whereas the lips of G. boninensis , G. confusa , G. confusoides , G. sabahensis , and G. shimizuana bear two longitudinal keels that arise from just below the ligulate apex, and those of G. appendiculata and G. nantoensis lack ridges altogether. In addition, both G. verrucosa and G. maliauensis possess columns that are nearly uniform in width from the base to apex, whereas the other species possess columns that are arguably widest at about one third of the length from the base. Therefore, when compared to members of the G. verrucosa complex, the new species is most similar to G. verrucosa , although it differs as described above.

Intriguingly, although G. holttumii was treated as a synonym of G. verrucosa by Seidenfaden & Wood (1992), O’Byrne (2010) reported that a fresh specimen from the type locality (Peninsular Malaysia) of G. holttumii matched the description and illustration of G. holttumii by Car (1929) but not those of G. verrucosa . Accordingly, Ong (2015) rejected Seidenfaden & Wood’s (1992) treatment of Gastrodia holttumii as a synonym of G. verrucosa and excluded Peninsular Malaysia from the distribution of G. verrucosa . Similarly, the specimens identified as G. verrucosa in other areas, such as Thailand ( Suddee & Harwood 2009) and the Philippines ( Pelser et al. 2011, Barcelona et al. 2013), may contain other undescribed species. However, because the precise identification of Gastrodia species requires the detailed analysis of floral organs that are concealed in the perianth tube, herbarium specimens will need to be reanalyzed to confirm the true identity of specimens previously attributed to G. verrucosa .

Figures

FIGURE 1. Gastrodia maliauensis (photos of the holotype). A. Flowers. B. Flower, side view. C. Dissected flower. D. Flattened perianth tube. E. Flattened perianth tube, with column. F. Lip. B–E. Bar = 5 mm. F. Bar = 1 mm.

FIGURE 2. Gastrodia maliauensis (drawn from the holotype). A. Habit. B. Flower, side view. C. Flower, bottom view. D. Flower, front view. E. Dissected flower. F. Flattened perianth tube. G. Lip. H. Column. I. Anther cap. A. Bar = 3 cm. B–F. Bar = 5 mm. G–I. Bar = 1 mm.