The rebuilding of an isolated rain forest assemblage: how disharmonic is the flora of Krakatau?
The compositional balance of the flora of the Krakatau Islands, Indonesia, is examined in order to identify taxonomic and/or ecological groups which are under-represented in this recovering island ecosystem in relation to regional analogues and potential source areas in the Sunda Strait (Ujung Kulon and Sebesi Island). Interpretations are conditioned by the limited availability of comparative data, the uncertainty surrounding dispersal classifications, the problem of determining habitat suitability for missing elements, and thus the unsuitability of a formal statistical approach. Analysis by dispersal syndrome supports predictions that species with large, winged, wind-scattered propagules, or those with no particular dispersal potential, are under-sampled. However, some species with winged propagules have colonized, in most cases probably by thalassochory (sea-dispersal). Although zoochorous (animal-dispersed) trees and shrubs are well represented on Krakatau, those large-seeded species which are primarily dependent on dispersal by animals other than birds are under-represented. Large-seeded zoochores are probably highly dependent on two species of Ducula (large fruit-pigeons) for transport to Krakatau and their colonization has been relatively slow. Comparison with Christmas and Jarak Islands yields differing degrees of overlap for thalassochorous, zoochorous, and anemochorous (wind-dispersed) spermatophytes and for pteridophytes, interpretable in terms of dispersability and size of the respective species pools. Particular families and genera can be identified which are seemingly under-sampled on Krakatau, as can some which are over-represented in relation to the principal comparative site, the Ujung Kulon peninsular, West Java. The latter are mostly very small-seeded wind-dispersed epiphytic herbs (especially orchids). Ferns are also very well represented in relation to the West Javan source pool. It is concluded that the flora of Krakatau remains disharmonic, in a predictable fashion, although it is certainly becoming less so. The data provide empirical evidence for the abilities of particular functional guilds of rain forest plants to disperse across significant barriers: the implications of these findings are discussed in relation to current concerns with forest fragmentation in the tropics.
WHITTAKER, R.J., JONES, S.H. AND PARTOMIHARDJO, T. (1997). The rebuilding of an isolated rain forest assemblage: how disharmonic is the flora of Krakatau?. Biodiversity and Conservation. 6 (12) pp. 1671-1696 [ DOI: 10.1023/A:1018335007666]