The First Record of Platycerium ridleyi in Sumatera

Abstract

Platycerium ridleyi Christ, one of the well-known staghorn ferns, was thought to be restricted to a few localities in Malaya, Singapore, northeastern Borneo, and the Lingga Archipelago. It was not known to occur on Sumatera (formerly Sumatra). In general, this species is regarded as rare (Ridley, 1926, p. 110); few collections have been made during the last 20 years, and according to Holttum (pers. comm.), this species must be regarded as extinct in Singapore. During some field trips in Jambi Province, Central Sumatera, in 1980, the authors visited two places where P. ridleyi appeared to be rather common. One locality is the Nature Reserve of Berbak along the river Air Hitam Laut (? 1?25'S, 104?30'E) about 15-25 km upstream from the east coast. The second locality is in the center of the island near Pasir Mayang, close to the head of the Batang Hari River (?+ ?0'S, 102?0'E), in a timber concession to P.T.I.F.A. (Asiatic Forest Industry, Ltd.), where the species may become extinct. These two places are rather far from each other, but fit well in the previously known distribution pattern. Platycerium coronarium (Konig ex Muller) Desv., the sister species of P. ridleyi, can be found in both P. ridleyi localities. The latter is a common and widely distributed species in the ever-wet lowlands of Malaya and the Greater Sunda Islands. Although the two species are closely related, they can be distinguished easily by their different habits. Platvcerium ridleyi has erect foliage fronds, an oval soral lobe, and entire base fronds (with very prominent veins) forming a large bulb. Platncerium coronarium has elongate, pendulous foliage fronds, a kidney-shaped soral lobe, and lobed base fronds forming a basket. There is another striking difference between the two species: P. ridlevi grows solitarily, but with many specimens in one tree (at least 10, mostly 15), whereas P. coronarium is present in one or two clusters, which are formed by vegetative reproduction. Ridley (1908, p. 56), who was the first author to distinguish P. ridleyi (as P. biforme var. erectum), mentioned its occurrence on lofty branches of trees like Shorea, at least 30 m above the ground. He never saw P. ridleyi and P. coronarium growing on the same tree. Furthermore, he cited Motley for specimens from Borneo, which were growing on the highest branches of trees in very exposed places. Holttum (1954, p. 140) remarked that P. ridleyi grows on tall trees, but sometimes also on low branches along rivers. It never grows in open country like P. coronarium. Corner (1978, p. 162) noted P. ridleyi to be frequent on high branches in swamp forests.