... it is not too much to say that when we have mastered
the difficulties presented by the peculiarities of island life
we shall find it comparatively easy to deal with the more
complex and less clearly defined problems of continental
distribution...
(Wallace 1902, p. 242)
These words taken from Alfred Russel Wallace’s
Island lifeencapsulate an over-arching idea that
could be termed the central paradigm of island bio-
geography. It is that islands, being discrete, inter-
nally quantifiable, numerous, and varied entities,
provide us with a suite of natural laboratories, from
which the discerning natural scientist can make a
selection that simplifies the complexity of the natu-
ral world, enabling theories of general importance
to be developed and tested. Under this umbrella, a
number of distinctive traditions have developed,
each of which is a form of island biogeography, but
only some of which are actually about the biogeog-
raphy of islands. They span a broad continuum
within ecology and biogeography, the end points of
which have little apparently in common. This book
explores these differing traditions and the links
between them within the covers of a single volume.
This book is divided into four parts, each of three
chapters. The first part, Islands as Natural
Laboratories, sets out to detail the properties of
these natural laboratories, without which we can
make little sense of the biogeographical data
derived from them. The second part, Island
Ecology, is concerned with pattern and process on
ecological timescales, and is focused on properties
such as the number and composition of species on
islands and how they vary between islands and
through time. The chapters making up the third
part, on Island Evolution, focus on evolutionary
pattern and process, at all levels from the instanta-
neous loss of heterozygosity associated with the
colonizing event on an island, through to the much
deeper temporal framework associated with the
great radiations of island lineages on remote
oceanic archipelagos like Hawaii. The final section
of the book, Islands and Conservation, incorporates
together two contrasting literatures, concerned
respectively with the threats to biodiversity derived
from the increased insularization of continental
ecosystems, and the threats arising from the loss of
insularization of remote islands.
We cannot begin our investigation of island
ecology, evolution, and conservation problems,
until we have explored something of the origins,
environments, and geological histories of the
platforms on which the action takes place. This
forms the subject matter of the second chapter,
Island environments. There are many forms of
‘islands’ to be found in the literature, from individ-
ual thistle plants (islands of sorts for the arthropods
that visit them) in an abandoned field, through to
remote volcanic archipelagos like the Galápagos
and Hawaiian islands (Fig. 1.1). The former are
very temporary islands in an ecological context,
and in practice, individual volcanic islands are also
quite short-lived platforms when judged in an
evolutionary time frame. The extraordinary
environmental dynamism of these remote
platforms requires much greater attention than it
has hitherto received in the island evolutionary
literature. Consider the following example. The
Juan Fernández archipelago consists of two main
islands, Masatierra, an island of 48 km^2 and 950 m
height, lying some 670 km from mainland Chile,
and Masafuera, an island of 50 km^2 and 1300 m3CHAPTER 1