Epirixanthes confusa Tsukaya, M. Suleiman & H. Okada, 2016

Tsukaya, Hirokazu, Suleiman, Monica & Okada, Hiroshi, 2016, A new species of Epirixanthes (Polygalaceaea) from Imbak Canyon, Sabah, Borneo, Phytotaxa 266 (2), pp. 146-150 : 147-149

Epirixanthes confusa Tsukaya, M. Suleiman & H. Okada , sp. nov. ( Figs. 1 , 2 )

Epirixanthes confusa differs from the other members of Epirixanthes in having the following features: persistent bracts even after fruit maturation, no bracteole, and pointed inflorescence apices.

Type — Malaysia. Sabah: Imbak Canyon Conservation Area, along the Ridge Trail, alt. 622 m, 05 o 01.099’ N, 117 o 01.774’ E, 9 August 2015, Tsukaya, H. Okada, H., Hayashi, T. & Suleiman, M., No. TOH-07 (Holo- BORH, iso- TI, KYO).

Erect mycoheterotrophic herb, 40–120 mm tall. Roots filamentous, branched. Stems reddish purple, branched, glabrous (rarely and scarcely having hairs). Leaves reduced to scale-like organs, 1.5–2.5 mm long, apex acute, glabrous. Shoots terminating in inflorescence, inflorescence spike, acutish at apex, 2.0– 4.5 cm (to>6.0 cm) long, 2.0– 2.5 mm thick, brownish ivory. Flowers dense, ivory (or white), ca. 2 mm long. Bracts purple-brownish ivory, linear-lanceolate, acuminate, longer than the flower bud, 1.0– 1.5 mm long, persistent. Sepals 5, having fine serrations along the margin, ovate-lanceolate, ca. 1.8 mm long, persistent. Petals 3, connate at base, middle lobe boat-shaped, obcordate, divided into two lobes at the tip. Stamens 5, filaments united, adnate at base to corolla. Ovary 2-locular, style straight or apically slightly curved upwards, stigma slightly 2-lobed. Fruit capsule, emarginate, enclosed in the sepals and bracts. Seeds, ca. 0.5 mm.

( A, B) Young ( A) and mature ( B) inflorescences. Note the persistent bracts. ( C) Albino form of E. confusa . (D) Flowering individual of E. elongata . Note caducous bracts, sparce inflorescence and hairs on stems, Photographs were taken in Imbak Canyon Conservation Area, on 8 August, 2015 ( A) and 9 August, 2015 ( B, C); in Betung-Kerihun National park, West Kalimantan, on 7 May, 2016.

Distribution — Found in the understories of dipterocarp forest, in particular along ridges. At present, E. confusa is known to occur only in Imbak Canyon, Sabah, Borneo. However, our preliminary surveys on herbarium specimens deposited in BO suggested that some specimens collected from Java, Indonesia, annotated as “ E. elongata ”, are actually E. confusa (for example, BO-1791084, BO-1794915, BO-1794902, BO-1478688, BO-1478690, BO-1794913 and BO-1794910). Because E. confusa is easily mis-identified as E. elongata , detailed re-examinations of herbarium specimens are required to reveal its whole distribution.

Diagnostis characters — Epirixanthes confusa resembles E. elongata in having a slender stature. Excluding E. elongata and E. confusa , all other Epirixanthes species show thick and round-headed inflorescences, and it is easy to distinguish them from E. elongata and E. confusa , which share acutish inflorescence tips. E. compressa also has a pointed inflorescence head ( Pendry, 2010), but shows abrupt changes in inflorescence thickness/diameter between zones in immature flower buds and in flowers, while E. elongata and E. confusa show smooth, gradual, and smaller size transitions, with respect to the diameter of inflorescences, from immature flower buds to flowers. The overall morphology is similar between E. elongata and E. confusa , but the presence of persistent bracts in the latter species is a clear distinguishing feature. Internodes between fruits do not elongate in E. confusa , giving an impression that the inflorescence at the fruiting stage seems to be denser than in E. elongata , where internodes between fruits elongate. The glabrous leaves also distinguish E. confusa from E. elongata that has pilose leaves ( Table 1).

Etymology— The species name E. confusa denotes the confusion between this species and E. elongata . Additional specimen examined — Malaysia. Sabah: Imbak Canyon Conservation Area, from Kuli Station

(N05 o 06’48”; E117 o 02’25”, alt. 312 m) to Kuli Water Fall (N05 o 00’344”; E117 o 03’208”) alt. 440 m. 8 August, 2015.

Tsukaya, H. Okada, H., Hayashi, T. & Suleiman, M., No. TOH-06 (BORH).

Figures

FIGURE 1. Epirixanthes confusa Tsukaya, M. Suleiman & H. Okada in its native habitat, in comparison with E. elongata.

FIGURE 2. Morphology of Epirixanthes confusa Tsukaya, M. Suleiman & H. Okada. A, Lateral view of a floral bud. B, Lateral view of a flower. C, Bract. D, Petals with stamens. Five anthers are usually arranged at the tip. E, Stigma and style. Stigma is slightly 2-lobed. F, Ovary. G, Mature fruit. H, Seed. I, Mature fruit with persistent sepals. J, Inflorescence. K, Flowering individual. Drawing by Ms. Kumi Hamasaki.