A Dwarf Livistona (Palmae) from Borneo

Abstract

Summary. A new palm species, Livistona exigua, is described from Borneo (Brunei), the first dwarf species known in the genus. Livistona is a genus of fan palms of about 28 species predominantly SE. Asian and Australian in distribution. The greatest diversity is found in Australia with about eleven species; here the genus ranges from tree palms up to 20-30 m tall down to shrub-like species (e.g. L. humilis R. Br.) with short stocky trunks to 5 m tall. In the Malesian rain forests Livistona is represented by tall tree palms only, these at maturity contributing in some way to the forest canopy, and this has hitherto appeared to be the constant aspect of the genus in these conditions. In the undergrowth another genus of Coryphoid palms, Licuala, has undergone extensive speciation; all except for one or two tree species (e.g. Licuala muelleri H. Wendl. & Drude) of Queensland are undergrowth species. Beccari (1933) noted that the genus Livistona was curiously absent from Borneo; since then, however, a representative from lowland swamp within the complex of L. saribus (Lour.) Merr., corresponding with L. hasseltii Hassk. of Java, has been found over a wide area of South Kalimantan (Indonesian Borneo) and herbarium specimens in Kew from Sandakan are apparently the same taxon. It was then most surprising to discover in the unmounted palm material at Kew a diminutive undergrowth Livistona collected by P. S. Ashton in 1959 in Brunei. This might easily have been passed over as a Licuala because of its small size were it not for the marked difference in leaf dissection between these two genera. In Livistona the lamina is partially divided up into compound or single-fold induplicate leaflets (i.e. V-shaped with margins adaxial, see Fig. Ic). The deepest splits normally extend only to about three-quarters of the radius of the lamina and are on the adaxial folds. Abaxial splitting occurs for a relatively short distance, producing cleft tips to the leaflets. In two species, Livistona loriphylla Becc. and L. decipiens Becc. from Australia, splits extend almost to the lamina base and there is a marked extension of the petiole into the lamina producing a typical 'costapalmate'