The Vegetation of Jarak Island, Straits of Malacca

Abstract

A qualitative and quantitative survey of the flora of Jarak, a small island 40 miles (64 km.) off the coast of Malaya in the Malacca Straits, has shown that there is little variety of spp. in comparison with the richness of the tropical lowland rain forest of the mainland and that certain families, common in the mainland forest, are either completely absent or poorly represented. In this respect the vegetation resembles that of an oceanic island, and an analysis of the normal expected method of seed dispersal of the higher plant species reveals that apart from 6 definite sea-borne spp., 2 man-introduced spp. and 3 wind-borne spp. with dust-like or plumed seed, they are, with exception of Tarrietia javanica, a sp. with large winged seed which was probably sea-dispersed, those distributed largely by birds and fruit-eating bats. The fauna is also restricted, consisting of only one resident mammal, a rat, presumably introduced by man. Reasons for this oceanic type of flora are discussed, and the submergence of island in volcanic ash from Toba in Sumatra, first suggested by Mr. M. W. F. Tweedie, Director of Raffles Museum, Singapore, is considered the most probable.