The role of animals in the colonization of the Krakatau Islands by fig trees (Ficus species)

Abstract

Abstract. 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 vascular plants. They now carry species‐poor mixed tropical forest, including some twenty‐three species of Ficus. Data on the sequence of colonization over the last century by twenty‐four Ficus species, twenty‐three species of volant frugivores, and by agaonid fig‐wasps, presumably from the large islands of Java and Sumatra, each some 44 km distant, are summarized. The potential of the volant frugivores as dispersers of fig seeds is assessed, the pollination problems involved in the colonization of islands by figs are reviewed and patterns of colonization by fig species and by their bird and bat dispersers are identified and discussed. In 1930 a new island, Anak Krakatau, emerged from Krakatau's submerged caldera. This active volcano suffered a self‐sterilizing eruption in 1952/1953 and has been colonized, under considerable constraint from its own volcanic activity, probably largely from the (selected) species pool present on Rakata, Sertung and Panjang, 2–4 km away. Its vegetation is at an earlier successional stage (grassland and Casuarina woodland) than that of the three older islands, and in 1992 the Casuarina 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, including preliminary assessments of the effects of pollinator limitation on 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.

Fruit Bats (Chiroptera: Pteropodidae) as Seed Dispersers and Pollinators in a Lowland Malaysian Rain Forest1

“…Shilton et al (1999) demonstrated that small captive pteropodids can retain viable Ficus seeds in their guts for more than 12 hours during the day when they are not feeding; however, because these bats were inactive during this period (Shilton et al 1999), the importance of this result to the long-distance dispersal of seeds is unclear. Nevertheless, the recolonization of the volcanic Krakatau islands by figs and other bat-dispersed taxa clearly demonstrates the importance of fruit bats for the long-distance dispersal of seeds (Whittaker & Jones 1994, Thornton et al 1996, Shilton et al 1999. Although fruit trees and feeding perches may still provide activity foci for most of the seed rain, because many fruit bat species defecate during flight, the overall seed shadows are likely to be relatively extended and more homogeneous compared to those produced for large, uningested seeds (Thomas 1982, Fleming 1988, Utzurrum 1995.…”

The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling

“…For example, transplant experiments of Arnica montana , have revealed that slug herbivory limits the lower elevational range of this subalpine plant (Bruelheide & Scheidel, 1999). Also, the colonization of islands by fleshy-fruited plants provides evidence that range limits and distributional areas of these species strongly depend on animal dispersers (Thornton, Compton & Wilson, 1996; Shanahan et al , 2001). …”

Fragmentation Effects on Diversity of Wasp Community and Its Impact on Fig/Fig Wasp Interaction in Ficus racemosa L.

“…The data of the present study and the other more data (Wang RW et al 2004, unpublished data) indicate that groups of trees are an important unit that keeps the structure of the wasp community stable. As a keystone plant resource in Southeast Asia and the Neotropics, figs support a broad spectrum of vertebrate frugivores during times of food scarcity in these areas (Krebs 1978;Thornton et al 1996;Nason et al 1998;Harrison 2003). Figs greatly affect the function and structure of the tropical rain forest (Sun 1992;Primack 1998) The present study has shown that the effect of fragmentation results in a different structure of the fig wasp community and that such an effect may change the position and function of figs in the fragmented area, thereby resulting in the development of different systems in the process of evolution.…”