Ecological aspects of plant colonisation of the Krakatau Islands

Abstract

Species assemblage data from the Krakatau Islands, Indonesia, are presented for the period 1883 to 1989 (including previously unpublished data from the 1989 sdrvey). Since 1934, 16 additional families of higher plants have colonised. Recent arrivals at the family level are mostly of zoochorous species of forest tree, indicating (subject to the effects of disturbance) a continuing increase in potential niche space within the island interiors. The data for Rakata (an uninterrupted prisere) conform to a successional explanation in which identifiable ecological groups of plants exhibit differing colonization and turnover patterns. Animal-dispersed canopy tree species and species which are widespread within the group, exhibit a very low probability of extinction once they have colonized successfully. There are, however, several constraints on the rapid spread of species within the group, in particular those connected to local dispersal (eg lack of large terrestrial mammals). In respect of dispersal to the group, partial survey data for the island of Sebesi from 1921 (revised) and 1989 provides the basis for comment as to the changing biogeographical circumstances of the Sunda Straits and the role of Sebesi as a 'stepping stone' island. The varied data discussed in the paper indicates that with the exception of the strand-line, no component of the Krakatau flora or vegetation has yet approached a stable composition. Both floral and faunal diversification are argued to be proximally controlled not only by dispersal opportunities but also by the dynamics of the dominant life-forms of the system, ie, the forest trees. Such hierarchical links, across trophic boundaries, should receive greater recognition in the construction of island biogeographical theory.

Primary Succession along an Elevation Gradient 15 Years after the Eruption of Mount Pinatubo, Luzon, Philippines

“…The long record of observation and high diversity make the Krakatau island group a center of biogeographic and successional investigation ( Whittaker et al 1992) as well as having provided critical insights into how dispersal limitations alter succession trajectories and the assembly of mature vegetation Jones 1994, Whittaker andFernán-dez Palacios 2007). However, those studies were conducted in dramatically different biological contexts (e.g., very few exotic species), and initial processes were observed only qualitatively.…”

Invasions of Plant Communities – More of the Same, Something Very Different, or Both?

“…Studies of Anak Krakatau, which emerged in the old caldera in 1930, have been detailed by several authors. The long record of observation and high diversity make the Krakatau Island group a center of biogeographic and successional investigation (Whittaker et al, 1989(Whittaker et al, , 1992Thornton, 1996). Studies of this group of volcanic islands have integrated succession with island biogeography and have provided significant insights into how dispersal limitations alter succession trajectories and the assembly of mature vegetation (Whittaker, 2004).…”

Colonization of Nishino-shima Island by Plants and Arthropods 31 Years after Eruption

“…On Rakata Island (in the Krakatau Islands), 120 plant species were present only 25 yr after the 1883 eruption (Whittaker et al 1992) (Table 2). Because Rakata Island is at least 85 times the size of Nishino-shima and is close (within 40 km) to large neighboring islands ( Java and Sumatra), the low barrier to dispersal makes the colonization process faster than on oceanic islands located farther from other sources of biota.…”