THE ROLE OF ANIMALS IN THE COLONIZATION OF THE KRAKATAU ISLANDS BY FIG TREES (FICUS SPECIES)

Since the biologically extirpating eruption of Krakatau (Sunda Strait) in 1883, Rakata (Krakatau's remnant) and two closely adjacent islands , Sertung and Panjang, have been colonized by over 200 species of vasc ular plants. They now carry species-poor mixed tropical forest, includ ing some twenty-three species of Ficus. Data on the sequence of coloni zation over the last century by twenty-four Ficus species, twenty-thre e species of volant frugivores, and by agaonid fig-wasps, presumably f rom the large islands of Java and Sumatra, each some 44km distant, are summarized. The potential of the volant frugivores as dispersers of f ig seeds is assessed, the pollination problems involved in the coloniz ation of islands by figs are reviewed and patterns of colonization by fig species and by their bird and bat dispersers are identified and di scussed. In 1930 a new island, Anak Krakatau, emerged from Krakatau's submerged caldera. This active volcano suffered a self-sterilizing eru ption in 1952/1953 and has been colonized, under considerable constrai nt from its own volcanic activity, probably largely from the (selected ) species pool present on Rakata, Sertung and Panjang, 2-4 km away. It s vegetation is at an earlier successional stage (grassland and Casual ina woodland) than that of the three older islands, and in 1992 the C asuarina woodland was in an early stage of transition to mixed forest. The colonization of Anak Krakatau by Ficus species, agaonid wasps and volant frugivores over a critical decade (1982-92) is reviewed, inclu ding preliminary assessments of the effects of pollinator limitation o n four pioneer fig species and indications of a possible effect of the presence of avian raptors, particularly the peregrine falcon, on fig colonization and forest diversification.