A new Globba with large white floral bracts from Peninsular Malaysia

Abstract Globba magnibracteata Y.Y.Sam, sp. nov. is described and illustrated. Colour plates, a preliminary conservation assessment and a discussion of its closely related taxa are provided.


Introduction
Globba is one of the largest genera in the Zingiberaceae family with over 100 species mostly found in the Indo-Chinese monsoon region. In Peninsular Malaysia, fourteen species, fi ve subspecies, eight varieties and a natural hybrid have been documented thus far (Newman et al. 2004;Sam et al. 2012). Th e genus is a common ground herb in the peninsula's tropical evergreen rainforest. Ridley (1924) provided the fi rst taxonomic account of the Peninsular Malaysian species. He has identifi ed twenty one species of which twelve were named by him. Holttum (1950), in his revision on the Zingiberaceae of Peninsular Malaysia, has changed some of Ridley's species to varietal rank or synonymised them and greatly reducing the number to ten species and ten varieties. A detailed cytological and morphological study by Lim (1972) has discovered a number of new specifi c and infraspecifi c taxa, bringing the total to twelve species, fi ve subspecies, eight varieties and one natural hybrid. Several new taxa continued to be named in the following years as plant collecting ventured further into the remote forested areas (Weber 1991;Ibrahim and Larsen 1995;Sam et al. 2012). Here in Peninsular Malaysia, we discovered another new species from the interior of Terengganu. Th is plant has remarkable large, white fl oral bracts which are well spaced on the long arching infl orescence. Th ese strongly refl exed sterile bracts are the largest amongst the peninsular species and this feature clearly distinguished it from others.
Th e current classifi cation of the genus recognises three subgenera, seven sections and two subsections based on the structure of the anther appendage (Williams et al. 2004). In Peninsular Malaysia, only the subgenus Globba, with four appendages and the two-appendage Ceratanthera have been recorded, none being from subgenus Mantisia. Twelve species, including the new G. magnibracteata belong to the subgenus Globba section Sempervirens, while only three are placed in the subgenus Ceratanthera.

Taxonomy
Globba magnibracteata Y.Y.Sam, sp. nov. urn:lsid:ipni.org:names:77158314-1 Figures 1-2 Diagnosis. Globba magnibracteata is similar to G. albobracteata N.E.Br. where both are placed in the subgenus Globba section Sempervirens. Th ey have the same vegetative morphologies and infl orescence structure but diff er in having wide spreading or strongly defl exed white sterile bracts versus the green appressed sterile bracts of G. albobracteata. Th e elliptic fertile bracts of G. magnibracteata are smaller (1.1-1.2 cm long) compared to the obovate bracts of G. albobracteata which are about 3 cm long. Th e cincinnus stalk of G. magnibracteata is also shorter (less than 1 cm) than that of G. 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 G. albobracteata.
Etymology. Th e epithet is derived from Latin and refers to the large (magnus) fl oral bract (bractea).
Distribution and ecology. Globba magnibracteata is only known from Jengai Forest Reserve, Peninsular Malaysia. Th e plants were found scattered on the shady and moist forest fl oor 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 aff ect the quality of the forest, especially the niche environment where the plants are to be found. Th e 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 G. magnibracteata was sighted. Th e area of occupancy for G. magnibracteata is only 4 km 2 plus its small population, thereby qualifying the species to be listed in the Critically Endangered category (IUCN 2016).
Notes. Globba magnibracteata closely resembles G. 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, infl orescence structure and fl ower colour. Th e diff erences lie in the sterile and fertile bracts, cincinni and fl oral parts. Globba magnibracteata has large white sterile bracts, which are wide spreading or defl exed, visible even at a far distance. Th e green sterile bracts of G. albobracteata are of similar size but they are appressed and overlapped on the peduncle making them not readily noticeable. Th e fertile bract is another distinguishable feature, G. magnibracteata having elliptic and smaller (1.1-1.2 cm) bracts compared to the obovate bracts of G. albobracteata, which are about 3 cm long. For the cincinni, the stalk of G. magnibracteata is clearly shorter, measuring less than 1 cm whereas it is 2-4 cm in G. albobracteata. In addition, the corolla lobes, lateral staminodes and labellum of G. magnibracteata are consistently smaller compared to G. albobracteata (Table 1). G. corneri (Weber, 1991) G. nawawii (Ibrahim & Larsen, 1995) Leaf number & position 9-13; spaced along leafy stem 9-11; spaced along leafy stem Globba cernua Baker is another species closely related to G. magnibracteata. Both grow in small clusters with 2-4 leafy shoots and their long infl orescences hang downwards in a very broad curve. Nevertheless, the distinctly white, large sterile bracts and the orange fl owers of G. magnibracteata immediately separate it from the small green bracts and pale yellow fl owers of G. cernua. Both sterile and fertile bracts of G. magnibracteata remain attached to the infl orescence but in G. cernua, the bracts are shed at the early stage of fl owering. Other diff erences 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: G. corneri A.Weber and G. nawawii H.Ibrahim & K.Larsen, which look similar to G. magnibracteata but there are several features which distinguish them (Table 1). Globba corneri diff ers from G. 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 G. 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 G. magnibracteata.
Th ere are several Th ai globbas with large showy fl oral bracts such as G. candida, G. laeta, G. siamensis, G. winittii, but they are not allied to G. magnibracteata. Th ese 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 fi nd these species in the evergreen forest of Peninsular Malaysia where G. magnibracteata grows.