KRAKATAU - COLONIZATION PATTERNS AND HIERARCHIES

The Islands of Krakatau, Indonesia, provide a study site where a 106-year history of primary colonization leading to the establishment of lowland tropical forest can be documented. The results of field studies of higher plant, butterfly and bird assemblages conducted since 1883 indicate that the forests have not attained maturity, continue to accumulate species, and that extinctions remain relatively rare events. Successional processes account for a great number of apparent species losses and some identifiable groups of colonists stand a better-than-average chance of long-term survival. The primary colonization of these islands is demonstrated to involve non-monotonic rate changes in observed immigration and extinction. Although motile and relatively short-lived organisms such as birds and butterflies may respond on relatively short time-scales, their hierarchical connections with plants link their patterns of colonization and turnover to the population and community dynamics of the dominant life forms of the system, i.e. to forest trees. The time-scale of response of the system is thus lengthened beyond reasonable expectations of environmental stasis. Simple notions of equilibria are thus shown to be inadequate in such complex ecosystems.