Dispersal, fruit utilization and seed predation of Dysoxylum gaudichaudianum in early successional rainforest, Krakatau, Indonesia

Abstract

ABSTRACTDysoxylum gaudichaudianum is an important canopy tree on the Krakatau Islands, and its ecology is of significance to an understanding of successional dynamics. It is abundant on Panjang and Sertung, but only locally common on Rakata. A study was undertaken of three aspects of its seed ecology in July/August 1992. The chief dispersers of D. gaudichaudianum are suggested here to be birds, with two species of pigeon and a bulbul prominent as fruit feeders over a short observation period. Bird activity dislodges large numbers of fruits and seeds which fall to the ground where they form a resource available to other animals. It was observed that seeds of D. gaudichaudianum suffer varying levels of attrition on the forest floor, with 40% of the total sample lost over a 12-day period, compared with 23% which had germinated. When mature, opening fruits develop a fishy aroma, which is attractive to insects. They hasten the decay process and release the seeds. The soft, rotting tissues of fallen fruits support a small, short-lived successional insect community. After about five days on the forest floor only the seeds and the outer fruit coat remain. Despite the abundance of fruit of this species during the dry season and its obvious attraction tó frugivorous birds, D. gaudichaudianum has still colonized only a small fraction of the near-coastal lowlands of Rakata.