out the less competitive supertramps. Before their
loss, however, the island acts to supply the
surrounding area with its surplus population, and
the species will therefore survive by having found
another defaunated island before being excluded
from the first. Diamond calculated that for some
supertramps the availability of Long island will
have enabled the quadrupling of the entire popula-
tion of the species. Long and Ritter thus hold
considerable interest. In Long’s case, this has been
added to recently by studies of the emergent island
Motmot, which has formed in the lake within Long
Island, providing a form of nested colonization
‘experiment’ (see Thornton et al. 2001).
5.4 Krakatau—succession, dispersal structure, and hierarchies
Background
Krakatau was the first site used by MacArthur and
Wilson to test their predictions of an approach to a
dynamic equilibrium. The natural recolonization
(Box 5.3) of the islands by birds between 1883 and
1930 appeared consistent with the EMIB: species
number reached an asymptote and further turnover
occurred (MacArthur and Wilson 1963, 1967).
However, the plant data from the islands revealed a
poorer fit, as species numbers continued to rise.
This was postulated to be due to one of two effects:
either that the pool of plant species was sufficiently
large to prevent a depletion effect on the immigra-
tion rate, or successional replacement of the pioneer
communities was incomplete, thereby leading to a
reduction in extinction rate for a time. The latter
effect was favoured, and illustrated in diagram-
matic form, but the EMIB was not modified
formally to account for the data.
Community succession
Although the first food chains to establish may well
have been of detritivores, and microorganisms, con-
sideration of the real business of community assem-
bly begins with the higher plants. Partial survey data
and descriptions of the plant communities are
available from often brief excursions in 1886,
1896/97, 1905–08, most years between 1919 and
1934, 1951, 1979, 1982/83, and 1989–95 (Whittaker
et al. 1989, 1992a; 2000). The system must be under-
stood both in terms of successional processes and in
relation to constraints on arrival and colonization.
The broad patterns of succession will be described
first.
The coastal communities established swiftly,
most of the flora being typical of the sea-dispersed
Indo-Pacific strand flora. In 1886, 10 of the 24
species of higher plants were strandline species. By
1897, it was possible to recognize a pes-capraefor-
mation (named after Ipomoea pes-caprae) of strand-
line creepers, backed in places by establishing
patches of coastal woodlands, of two characteristic
types. First, patches which were to become repre-
sentative of the so-called Barringtoniaassociation
(more generally typified by the tree Terminalia cat-
appa), another vegetation type typical for the
region, and secondly, stands of Casuarina equisetifo-
lia. The latter is a sea- and wind-dispersed pioneer-
ing tree species, which also occupies some
precipitous locations further from the sea. In the
coastal areas it typically lasts for just one genera-
tion, as it fails to establish under a closed forest. It
is notable that as early as 1897 the coastal vegeta-
tion types were already recognizable as similar to
those of many other sites in the region (Ernst 1908).
The coastal communities continued to accrue
species over the following two decades, but have
since exhibited relatively little directional composi-
tional turnover, apart from the loss in many areas of
Casuarina. They may thus be described as almost an
‘autosuccession’ (Schmitt and Whittaker 1998).
In the interiors, a much more complex sequence
of communities has unfolded. To varying degrees
this can be understood in relation to the consider-
able differences in habitats between and within
islands, to differential landfall of plant species
within the group, and to the dynamics of the
physical environment, especially the disruption
originating from the new volcanic island, Anak
Krakatau. In 1886, most of the cover in the interior
was supplied by 10 species of ferns, accompanied
by 2 species of grass and 2 members of the
Asteraceae: all 14 species being wind-dispersed. By
1897, the interiors had become clothed in a denseKRAKATAU—SUCCESSION, DISPERSAL STRUCTURE, AND HIERARCHIES 131