Globba magnibracteata Y.Y.Sam, 2016

Sam, Yen Yen & Ibrahim, Halijah, 2016, A new Globba with large white floral bracts from Peninsular Malaysia, PhytoKeys 73, pp. 117-124 : 118-121

Globba magnibracteata Y.Y.Sam sp. nov. Figures 1 , 2

Diagnosis.

Globba magnibracteata is similar to Globba albobracteata N.E.Br. where both are placed in the subgenus Globba section Sempervirens . They have the same vegetative morphologies and inflorescence structure but differ in having wide spreading or strongly deflexed white sterile bracts versus the green appressed sterile bracts of Globba albobracteata . The elliptic fertile bracts of Globba magnibracteata are smaller (1.1-1.2 cm long) compared to the obovate bracts of Globba albobracteata which are about 3 cm long. The cincinnus stalk of Globba magnibracteata is also shorter (less than 1 cm) than that of Globba albobracteata (2-4 cm). Globba magnibracteata has bulbils with many roots and one bamboo-like shoot distinct from the one-root-one-shoot bulbils in Globba albobracteata .

Type.

MALAYSIA. Peninsular Malaysia, Terengganu, Jengai Forest Reserve, Compartment 5, 4°39.59'N, 103°05.05'E, 21 April 2009, Sam & Aidil FRI 68959 (holotype: KEP; isotypes: E, KLU, SAN, SING)

Description.

Rhizomatous herb, evergreen, 30-70 cm tall, in small clumps of 3-4 leafy stems. Rhizome c. 5 mm diameter, not tuberous. Leafy stems bend on a large curve, basal stem slightly swollen; base to first leaf (18-) 25-32 cm long; first leaf to the uppermost leaf sheath (32-) 42-54 cm long; bladeless sheaths 3-4, pubescent, persistent, lower sheaths purplish when young; leaf sheath pubescent; ligule truncate, pubescent, persistent, 1-2 mm long; leaves 9-13, 3-6 cm apart, almost sessile; lamina narrowly ovate to elliptic, (14)17-22 × (3.8) 4.3-6.7 cm, adaxial dark green with slightly raised lateral veins, glabrous, abaxial pale green, pubescent, base cuneate, apex attenuate with long acumen. Inflorescence terminal, 13.2-17 cm long, bent downwards in a very broad curve, rachis pointing perpendicularly down; peduncle 9.5-11 cm long, green, pubescent, with 4-6 large sterile bracts positioned at the middle part only; sterile bracts elliptic-oblong, largest 4.5-6.5 × 0.7-1.2 cm, white, pubescent, persistent, spreading to strongly reflexed, very lax; rachis 2.7-7 cm long, axis green, pubescent, 7-17 cincinni, lax; fertile bracts elliptic, 11-12 × c. 4 mm, white, pubescent, spreading to reflexed, persistent; cincinni 6-22 mm long, pubescent, up to 8 mm long to first flower; bracteoles boat shaped, 3-4 mm long, orange. Flowers orange, up to 14 flowers on each cincinnus; pedicel c. 1 mm, green, pubescent; calyx tubular, 3-4 mm long, pubescent, apex trilobed; corolla tube 14-15 mm long, pubescent; dorsal corolla lobe c. 5 mm long, concave, apex hooded, abaxial hairy; lateral corolla lobes c. 4 × 2.5 mm, broadly elliptic, apex rounded, margin curved in when fresh, abaxial hairy; lateral staminodes narrowly ovate, c. 5 × 1.5 mm, same length as corolla lobes, spreading, apex acuminate; labellum 5-6 mm long, 2 brown spots in the centre, base bifid, c. 4 mm wide, lobes divergent. Stamen filament c. 17 mm long; anther c. 2 mm long, with 4 appendages; appendages triangular, c. 2.5 × 1 mm, spreading wide. Ovary c. 2 mm long, orange, pubescent, unilocular; stigma c. 1 × 1 mm, clavate, ciliate, ostiole transverse, facing upwards; epigynous glands linear, 2, c. 4 mm long. Fruits globose, glabrous, pale green when young; seeds not observed. Bulbils at the position of last flower in cincinni, many roots and shoots but only one developed into bamboo-like shoot.

Etymology.

The epithet is derived from Latin and refers to the large (magnus) floral bract (bractea).

Distribution and ecology.

Globba magnibracteata is only known from Jengai Forest Reserve, Peninsular Malaysia. The plants were found scattered on the shady and moist forest floor with a thick humus layer in the lowland dipterocarp forest, a tropical evergreen rainforest.

Preliminary conservation assessment.

Critically Endangered, CR B2ab(iii). Globba magnibracteata is only found in Compartment 5 in the Jengai Forest Reserve which is a production forest subjected to selective logging on a rotation basis. Timber harvesting will inevitably and adversely affect the quality of the forest, especially the niche environment where the plants are to be found. The population is also very small, less than 20 mature individuals being encountered at the site. Although several extensive botanical collections in other compartments in the same reserved forest were undertaken, no Globba magnibracteata was sighted. The area of occupancy for Globba magnibracteata is only 4 km2 plus its small population, thereby qualifying the species to be listed in the Critically Endangered category ( IUCN 2016).

Notes.

Globba magnibracteata closely resembles Globba albobracteata from Sumatra, Indonesia. Both have about 5-6 pairs of leaves spaced widely on the slender leafy stems and are also similar in lamina shape and size, inflorescence structure and flower colour. The differences lie in the sterile and fertile bracts, cincinni and floral parts. Globba magnibracteata has large white sterile bracts, which are wide spreading or deflexed, visible even at a far distance. The green sterile bracts of Globba albobracteata are of similar size but they are appressed and overlapped on the peduncle making them not readily noticeable. The fertile bract is another distinguishable feature, Globba magnibracteata having elliptic and smaller (1.1-1.2 cm) bracts compared to the obovate bracts of Globba albobracteata , which are about 3 cm long. For the cincinni, the stalk of Globba magnibracteata is clearly shorter, measuring less than 1 cm whereas it is 2-4 cm in Globba albobracteata . In addition, the corolla lobes, lateral staminodes and labellum of Globba magnibracteata are consistently smaller compared to Globba albobracteata (Table 1 ).

Globba c ernua Baker is another species closely related to Globba magnibracteata . Both grow in small clusters with 2-4 leafy shoots and their long inflorescences hang downwards in a very broad curve. Nevertheless, the distinctly white, large sterile bracts and the orange flowers of Globba magnibracteata immediately separate it from the small green bracts and pale yellow flowers of Globba cernua . Both sterile and fertile bracts of Globba magnibracteata remain attached to the inflorescence but in Globba cernua , the bracts are shed at the early stage of flowering. Other differences were also observed upon closer examination, such as the number of leaves and size of the staminodes (Table 1 ).

Among the Globba species in Peninsular Malaysia, there are two species with conspicuous white bracts: Globba corneri A.Weber and Globba nawawii H.Ibrahim & K.Larsen, which look similar to Globba magnibracteata but there are several features which distinguish them (Table 1 ). Globba corneri differs from Globba magnibracteata in the following characteristics: leafy stems with two leaves crowded at terminal, short peduncle that bend abruptly downwards, large white fertile bracts and the lateral staminodes are twice the length of the corolla lobes. For Globba nawawii , it has fewer leaves, longer rachis, smaller sterile and fertile bracts and lateral staminodes twice the length of the corolla lobes compared with those Globba magnibracteata .

There are several Thai globbas with large showy floral bracts such as Globba candida , Globba laeta , Globba siamensis , Globba winittii , but they are not allied to Globba magnibracteata . These plants thrive in the seasonal forest and their leafy parts die back during the dry season leaving the rhizome dormant underground. It is not possible to find these species in the evergreen forest of Peninsular Malaysia where Globba magnibracteata grows.

Figures

Figure 1. A-D Globba magnibracteata A Habit B Ligule C Inflorescence D Sterile floral bracts E Flower F Bulbils G Flowers of Globba corneri, Globba nawawii and Globba magnibracteata H Globba albobracteata I Globba cernua J Globba corneri K Globba nawawii. (Photographs A-G, I and K by Y. Y. Sam, H by A. Takano, J by Y. M. Chan).

Figure 2. Globba magnibracteata Y. Y. Sam A Habit B Inflorescence C Sterile bract D Bracteole E Flower F Ovary and calyx G Dorsal corolla lobe in front and side view H Lateral corolla lobe in ventral and side view I Lateral staminodes in ventral and side view J Labellum K Anther appendages L Stigma. Drawn by M. N. Aidil from Sam & Aidil FRI 68959 (KEP).