SPECIALISSUE
Four Darwinian themes on the origin,evolution and preservation of islandlife
Mark V. Lomolino*
‘As with shipwrecked mariners near a coast, it would have been
better for the good swimmers if they had been able to swim still
further,…’
‘A gun is here almost superfluous...’
‘It is impossible to reflect on the changed state of the American
continent without the deepest astonishment.’
‘Humboldt saw in South America a parrot which was the sole living
creature that could speak a word of the language of a lost tribe…’
INTRODUCTION
The above excerpts of quotations from Charles Darwin’s
writings, which I present and discuss in detail below, capture
themes that proved seminal for generations of scientists who
were equally captivated by both the marvels and the perils of
island life. Although presented as I have done so above as
disarticulated and seemingly unrelated metaphors and observa-
tions, these passages from Darwin’s publications serve as mile
markers along a professional and personal journey shared by
most scientists who study island life: one that progresses from an
innate attraction for insular biotas, to an astonishment over their
distinct and seemingly bizarre character, a quest to explain these
phenomena in the most fundamental terms, and finally to a
sobering understanding of the fragility of island life and of our
obligations as scientists and the planet’s only global stewards to
conserve these imperilled biotas.
Darwin, of course, was not the first naturalist to study the
diversity and singular nature of island life, but his classic works
clearly constitute a seminal nexus in the reticulating phylogeny
of island theory. Perhaps just as important, Darwin remarked
on the decline of nature over a century before ‘biodiversity’
and ‘conservation biology’ were first articulated.
Here I provide an historical and prospective overview of the
development of theory on the ecological and evolutionary
assembly of insular biotas and, in particular, the continuing
capacity of island studies to provide fundamental insights for
conserving the diversity and natural character of native biotas.
In forming his theory of natural selection, Darwin drew heavily
on studies of the effects of artificial selection on domestic
livestock. Thus, I see fitting irony and symmetry in the
prospect that the tables should now be turned; that our
abilities to predict and hopefully mitigate the effects of
artificial selection incurred through species introductions,
overharvesting and anthropogenic insularization (via habitat
loss and fragmentation) rest heavily on the revelations of
Darwin and generations of countless others who studied the
effects of natural selection on isolated biotas. The relevance of
island studies is only likely to increase as their native biotas
become ever rarer, and as an increasing proportion of
continental biotas become more restricted to island-like
ecosystems (e.g. wildlife parks, nature reserves and other rem-
nants of once expansive and continuous, native ecosystems).
My purpose here is to discuss four themes inspired by the
research and writings of Charles Darwin; themes on the
assembly (and disassembly) of insular biotas which continue to
hold great promise for providing insights into their ecological
and evolutionary development, and for conserving the natural
character and evolutionary potential of species restricted to
isolated ecosystems (natural or anthropogenic). The first
theme describes how selective pressures on islands are often
College of Environmental Science and Forestry,
Syracuse, NY 13210, USA
*Correspondence: Mark V. Lomolino, College of
Environmental Science and Forestry, Syracuse,
NY 13210, USA.
E-mail: [email protected]
ABSTRACT
Charles Darwin’s observations and insights continue to inspire nearly all scientists
who are captivated by both the marvels and the perils of island life. Here I feature
four themes inspired by Darwin’s singular insights: themes that may continue to
provide valuable lessons for understanding the ecological and evolutionary
development of insular biotas, and for conserving the natural character and
evolutionary potential of all species restricted to isolated ecosystems (natural or
anthropogenic).
Keywords
Assembly, biogeography, Charles Darwin, conservation, evolution, extinction,
islands.
Journal of Biogeography (J. Biogeogr.) (2010) 37, 985–994
ª 2009 Blackwell Publishing Ltd www.blackwellpublishing.com/jbi 985doi:10.1111/j.1365-2699.2009.02247.x
reversed from those in species-rich, taxonomically balanced
communities of the continents. The second and third themes
address resultant effects of those reversals in selection forces,
including the development of naıvete and the fragility of
insular biotas, and the downsizing (through megafaunal
extinctions) and evolutionary convergence on phenotypes that
are optimal in species-poor and disharmonic communities of
remote, oceanic islands. The final theme addresses the
geography of extinction which, seemingly paradoxically to
the general fragility of insular biotas, is characterized by
persistence of the most isolated populations.
Most examples and case studies that I discuss here are of
terrestrial systems, especially vertebrates. I leave it to others to
explore the heuristic and applied relevance of these themes to
other ecosystems and taxa.
FOUR DARWINIAN THEMES ON THE ASSEMBLY
OF INSULAR BIOTAS
Theme 1. Reversals in natural selection: from
‘swimming’ to ‘sticking to the wreck’
‘As with shipwrecked mariners near a coast, it would have been
better for the good swimmers if they had been able to swim still
further, whereas it would have been better for the bad swimmers if
they had not been able to swim at all and had stuck to the wreck.’
(Darwin, 1859, p. 177)
I begin with the above passage from The Origin because it
provides a conceptual framework fundamental to understand-
ing the ecological and evolutionary assembly of island life:
reversals in selective pressures which produce both the marvels
and perils of island life. Darwin used the first part of this
metaphor to explain a type of natural selection quite different
from ‘survival of the fittest’. That is, he envisioned this form of
natural selection occurring during immigration to very isolated
islands, and resulting in founding populations biased in favour
of individuals with superior immigration abilities. Unlike drift
and random founding effects, immigrant selection (sometimes
termed ‘selection for thrifty genotypes’ by anthropologists;
Neel, 1962) can explain directional trends in the structure of
insular communities and populations (e.g. towards dishar-
mony and dominance of particular, highly vagile species or
phenotypes: see Darlington, 1957; Carlquist, 1966a,b; Lomo-
lino, 1984, 1993; and Bindon & Baker, 1997).
Of even more fundamental importance in terms of under-
standing the special nature of insular biotas is the second part
of Darwin’s metaphor because it cogently asserts that selective
pressures vary – but in a very predictable manner – both
among species and across the stages of ecological and
evolutionary assembly of insular biotas. Indeed, Darwin was
using the above metaphor to explain some intriguing reversals,
paradoxes and anomalies of island life, including the many
reports from archaeologists and neo-naturalists such as Sir
Richard Owen, who described endemic birds of remote
oceanic islands such as dodos, moas and elephant birds that
totally lacked the power of flight.
‘As Professor Owens has remarked, there is no greater anomaly in
nature than a bird that cannot fly.’
(Darwin, 1859, pp. 175–176)
The anomaly, however, was rendered explicable by Darwin’s
eloquent metaphor of shipwrecked mariners. The natural
ontogeny of island endemics is one of regular and highly
predictable reversals in natural selection from that for the ‘good
swimmers’ during immigration, to selection for those adapted to
the special nature of insular environments following coloniza-
tion. Many hundreds of birds, insects and plants – in succumb-
ing to the pressures for ‘sticking to the wreck’ – ultimately lost
the capacity to disperse to other islands (see McNab, 1994).
Theme 2. The perils of splendid isolation
‘A gun is here almost superfluous; for with the muzzle I pushed a
hawk off the branch of a tree.’
(Darwin, 1860, Ch. 17, Galapagos Archipelago)
Reversals in natural selection are at the heart of explanations
for not only the many marvels of island life, but its fragility as
well. That is, selection for adaptation to the special nature of
insular environments – which include not just their isolation
and limited area, but the depauperate and disharmonic nature
of their communities – results in fundamental transformations
in the character of insular species. In addition to the striking
anomalies of flightless birds and insects discussed by Darwin
and many others, these transformations include a suite of
equally remarkable reversals in morphology, physiology and
behaviour in countless other species – ecological and evolu-
tionary adaptations of insular species to remote island
communities, which are typically free of terrestrial mammals.
Under these conditions, both plants and animals often lose the
structures and behaviours essential for predator (carnivore and
herbivore) avoidance on the mainland (Carlquist, 1965, 1974;
Lomolino et al., 2006; Whittaker & Fernandez-Palacios, 2007).
On the mainland, interspecific interactions in species-rich
and ecologically balanced communities can drive ecological
and evolutionary divergence among species; some plants
avoiding competition and herbivory by dispersing to colonize
ephemeral habitats and growing and reproducing rapidly (as
herbaceous forms), others investing more in arsenals of thorns
and defensive chemicals. In animals, divergence in body size on
the continents may be in response to selective pressures to
reduced competition or escape predators; e.g. some species
decreasing in size and thus becoming more capable of finding
shelter in burrows or under rocks and logs; others increasing in
size and simply outgrowing their would-be predators; and still
others reducing predation risks by becoming more vigilant,
more swift of foot or, in the case of bats and birds, true fliers.
On islands, however, interspecific interactions and associated
selective pressures are dramatically reduced – shifting towards
those associated with more intense competition from conspe-
cifics and a very limited and disharmonic group of other
insular residents (dominated by the biota of long-distance
dispersal and their descendants).
M. V. Lomolino
986 Journal of Biogeography 37, 985–994ª 2009 Blackwell Publishing Ltd
In his account of the voyage of the Beagle, Darwin described
the naıvete and fragility of island life, and warned of the perils
of species introductions being conducted by European explor-
ers and colonists as they tamed and transformed even the most
remote archipelagos across the globe.
‘A gun is here almost superfluous; for with the muzzle I pushed a
hawk off the branch of a tree. One day, whilst lying down, a
mocking-thrush alighted on the edge of a pitcher made of the shell
of a tortoise, which I held in my hand, and began very quietly to sip
the water; it allowed me to lift it from the ground whilst seated on
the vessel: I often tried, and very nearly succeeded, in catching these
birds by the legs.’
‘We may infer from these facts, what havoc the introduction of any
new beast of prey must cause in a country, before the instincts of the
indigenous inhabitants have become adapted to the stranger’s craft
of power.’
(Darwin, 1860, Ch. 17, Galapagos Archipelago)
The fragility of island life is all too well documented in the
record of historic extinctions of plants and animals, which is
characterized by a highly disproportionate loss of insular vs.
mainland forms (Fig. 1); most of this resulting from introduced
species (including humans) who devastated native insular biotas
before they could adapt to what Darwin described as the
‘stranger’s craft of power’. Even in more recent times, when the
rate of extinctions on the continents now rivals that of islands
(Fig. 2), extinctions may again be insular in nature; in this case
because invading human civilizations and technologies have
converted once expansive continental landscapes to archipelagos
of remnant habitats isolated within seas of anthropogenic
ecosystems (see also Ellis & Ramankutty, 2008).
Theme 3. Megafaunal extinctions and body size
convergence
Well before conservation biology became an established
discipline, and perhaps over a century before the term
‘biodiversity’ was coined, Darwin and his contemporaries
observed that nature was in decline, much of it for the same
reasons outlined above – artificial (anthropogenic) selection,
including species introductions, conversions of native habitats,
and over-harvesting. Thus, in 1839 he observed that:
‘It is impossible to reflect on the changed state of the American
continent without the deepest astonishment. Formerly it must have
swarmed with great monsters: now we find mere pigmies, compared
with the antecedent, allied races.’
(Darwin, 1839, p. 448)
Darwin went on to correct an earlier proposition of the
distinguished naturalist of the previous century, Georges-Louis
Leclerc, Comte de Buffon. Again, Darwin was invoking the
principle of reversals in natural selection, but this time
referring to its effects on continental biotas during prehistoric
periods (i.e. during aboriginal colonization of the New World
and subsequent collapse of its megafauna):
‘… If Buffon had known of the gigantic sloth and armadillo-like
animals, and of the lost Pachydermata, he might have said with
greater semblance of truth that the creative force in America had
lost its power, rather than that it had never possessed great vigour.’
(Darwin, 1839, p. 448)
Darwin was reacting to Buffon’s unfortunate explanation for
the distinctiveness and apparent diminutive nature of the
North American fauna:
‘In this New World, … there is a combination of elements and other
physical causes, something that opposes amplification of Nature.’
‘There are obstacles to the development, and perhaps to the
formation of large germs … [persisting forms that] shrink under the
niggardly sky and an unprolific land, thinly peopled with wandering
savages.’
(Buffon, 1766)
Buffon envisioned that the distinctiveness among continen-
tal biotas (a pattern so fundamental to biogeography that
it eventually became known as Buffon’s law) results from
divergence in isolation, with some forms advancing or being
amplified while others degenerate in response to conditions of
Figure 1 The fragility of island life is clearly evidenced in the
disproportionate number of extinctions of insular vs. continental
plants and animals over the past 500 years (from Lomolino et al.,
2006; after Reid & Miller, 1989).
Figure 2 The rise in extinction rates of continental animals (in
particular, mammals, molluscs and birds) relative to those on
oceanic islands over the most recent decades may again be insular
in nature, as once expansive continental systems have been insu-
larized by habitat conversion and expansion of anthropogenic
ecosystems (from Lomolino et al., 2006; after World Conservation
Monitoring Centre, 1992).
Four Darwinian themes
Journal of Biogeography 37, 985–994 987ª 2009 Blackwell Publishing Ltd
their environments (i.e. those of the New World). As we know
today, palaeontologists have uncovered irrefutable evidence in
favour of Darwin’s views: the long-isolated continents of the
New World, along with Australia and large islands, were in the
not-so-distant past inhabited by their own megafauna, in
many cases rivalling that of vertebrate assemblages still
persisting in Africa and other regions of the Old World
tropics. Not surprisingly, Alfred Russel Wallace’s views on this
point were entirely consistent with those of Darwin:
‘We live in a zoologically impoverished world, from which all the
hugest, and fiercest, and strangest forms have recently disappeared.’
(Wallace, 1876, p. 150)
These episodes of megafaunal collapse provide additional
evidence for the importance of anthropogenic reversals in
selective forces; in this case from those prevailing throughout
much of the late Cenozoic – which favoured the formation of
‘large germs’, to the reversals that caused their extinctions during
the latter stages of the Pleistocene. These megafaunal extinctions
were probably the result of repeated range expansions and
colonization by ecologically significant humans and subsequent
artificial selection against the giants and other marvels of
evolution in isolation (see Flannery, 1994; Grayson & Meltzer,
2003; Barnosky et al., 2004; Martin, 2005; Gillespie, 2008). The
ultimate results of colonizations by exotic, human civilizations
were entire assemblages that have been downsized through
species selection (i.e. the loss of their largest species), and
possibly through microevolutionary downsizing of surviving
forms as well. Flannery (1994) has termed this latter process
‘time-dwarfing’, and he provides some intriguing putative
examples. Following the colonization of Australia by aborigines
some 55,000 to 60,000 years bp, all the mega-marsupials greater
than 400 kg suffered extinction, while all those smaller than 5 kg
were apparently spared. Many of those of intermediate size did
survive, but in altered form with the most pronounced cases of
time-dwarfing occurring in the largest surviving species (the
body mass of red and grey kangaroos decreasing by about 30%,
while that of much smaller species such as spotted quolls and
rock wallabies declined by less than 10%; see Flannery, 1994, pp.
208–216; and Lomolino et al., 2006, p. 559; but see Price, 2008).
These patterns in species selection and body size evolution
of the surviving megafauna on the island continent of Australia
are similar to those reported for many vertebrates on true
islands. Just as for continental biotas, the list of the world’s
extinct and endangered insular species comprises a dispropor-
tionate number of large animals including megafaunal tor-
toises, snakes and lizards, along with many species of large,
flightless birds [e.g. the dodo (Raphus cucullatus) of Mauritius,
the solitaires (Raphus solitarius and Pezophaps solitariaon) of
Reunion and Rodriguez, the elephant birds (Aepyornithidae)
of Madagascar and the moas (Pachyornis spp.) of New
Zealand]. The collapse of New Zealand’s 10 to 15 species of
moas is an exemplary case of size-selective extinctions, with the
sequence of extinctions generally progressing from the largest
to smallest species following colonization of the islands by the
Maori people (Worthy & Holdaway, 2002).
On isolated, small or otherwise depauperate islands, the
mammals and other terrestrial vertebrates that do persist tend to
exhibit a pattern of evolutionary convergence termed the island
rule, with small species increasing in size and large (including
megafaunal) species decreasing in size (Fig. 3a; see Lomolino,
1985, 2005). The pattern is quite general and, despite much
variation within and among various groups of mammals, most
exhibit the trend of convergence towards an intermediate body
size (Fig. 3b; but see Meiri et al., 2004; and Meiri, 2007). The
pattern is reported for other terrestrial vertebrates, including
insular birds (Clegg & Owens, 2002) and reptiles (Boback, 2003;
Boback & Guyer, 2003; but see Meiri, 2007, 2008, and Hedges,
2008), and for marine gastropods inhabiting isolated regions of
the deep sea (McClain et al., 2006) and nine-spined sticklebacks
(Pungitius pungitius) inhabiting small ponds lacking their key
predators (Herczeg et al., 2009). This phenomenon also appears
to be ancient – being exhibited in insular mammals during
Pliocene to Holocene times (Fig. 3b; for a possible example in
insular hominids see Brown et al., 2004, and Morwood et al.,
2004) and possibly in insular sauropods as well (Jianu &
Weishampel, 1999; Sander et al., 2006).
A related phenomenon and response to the depauperate and
disharmonic nature of remote islands is ecological and
evolutionary release in the form of ‘super-generalists’ (sensu
Olesen et al., 2002). On remote, species-poor islands, some of
the inhabitants may increase their niche breadths and symbi-
otic capacities to adapt and interact (e.g. as generalist
pollinators and seed dispersers) with a relatively high number
of species in comparison to their mainland ancestors. As
Olesen & Valido (2003) have shown, super-generalists on
islands often include lizards, which rarely serve as pollinators
and dispersal agents on the mainland. For example, of the
world’s lizard species, some 95% of those known to visit
flowers (and presumably serve as pollinators) and 63% of
those known to feed on fruit (dispersing their seeds)
are insular forms. These interrelated island phenomena – of
super-generalists and unusual pollinators and dispersal agents,
probably result from density overcompensation of lizard
populations and lower predation risks, both of these associated
with the absence or paucity of non-volant mammals, selected
arthropods and other competitors, pollinators and predators
on remote islands.
One very important lesson from these case studies in the
ecological and evolutionary assembly of insular biotas is that
reversals in natural selection, whether natural or anthropo-
genic, can fundamentally transform both the diversity and the
natural character of native biotas.
Theme 4. Humboldt’s parrot: the geography of
extinction in man and beasts
Perhaps one of the most surprising if not astounding of
Darwin’s observations discussed here is his reference to one
of Alexander von Humboldt’s discoveries. Although seem-
ingly an aside to Humboldt’s more broadly recognized and
seminal contributions (see Jackson, 2009), he describes a
M. V. Lomolino
988 Journal of Biogeography 37, 985–994ª 2009 Blackwell Publishing Ltd
(b)
(a)
Figure 3 The island rule describes a graded trend from gigantism in small species to dwarfism in large species of insular vertebrates:
(a) extant, insular mammals, (b) other insular vertebrates, including those of true islands and other isolated ecosystems. Si is calculated as
mass of the insular population divided by that of its closest, mainland relative (sources: mammals of fragmented forests – Schmidt & Jensen,
2003; insular birds – Clegg & Owens, 2002; extant, non-volant mammals – blue line, from data graphed in panel (a); Australian time dwarfs –
Flannery, 1994; extinct ungulates and proboscideans – Raia & Meiri, 2006, body masses from M. R. Palombo, Universita ‘‘La Sapienza’’,
Roma, Italy, pers. comm. 2009; snakes – Boback & Guyer, 2003; turtles – N. Karraker, College of Environmental Science and Forestry,
Syracuse, NY, USA, pers. comm. 2004; bats – Krzanowski, 1967).
Four Darwinian themes
Journal of Biogeography 37, 985–994 989ª 2009 Blackwell Publishing Ltd
phenomenon that is identical in most respects to patterns
only recently emerging from modern studies on the geogra-
phy of extinction.
‘Humboldt saw in South America a parrot which was the sole living
creature that could speak a word of the language of a lost tribe.
Ancient monuments and stone implements found in all parts of the
world, of which no tradition is preserved by the present inhabitants,
indicate much extinction. Some small broken tribes, remnants of
former races, still survive in isolated and generally mountainous
districts.’ [bold added here for emphasis]
(Darwin, 1871, p. 252)
Beyond the truly remarkable preservation in the grey matter
of a parrot of approximately 40 cognate phrases of this now
extinct culture, Darwin’s account accurately describes geo-
graphic range collapse, not just in other human populations
such as the Incas and Anasazi, but across a broad diversity of
other species as well (Lomolino & Channell, 1995; Channell &
Lomolino, 2000; Gaston, 2003; Laliberte & Ripple, 2004). The
final refugia of collapsing biotas tend to be located along the
most isolated reaches of their historical geographic range:
along its periphery, on mountaintops, or islands (Fig. 4).
These are the last sites to be contacted and eventually
overwhelmed by extinction forces, which spread like a
contagion across native landscapes and seascapes. As a result,
many of the once broadly distributed but now imperilled
continental species have become insularized: restricted to
anthropogenic archipelagos of remnant habitats, isolated from
other remnant populations and restricted to geographically
limited and ecologically simplified ecosystems.
Patterns of geographic range collapse for exclusively insular
species, such as Hawaiian birds, plants and snails, represent
apparently anomalous but especially instructive case studies.
Rather than persisting along the periphery of the species’
ranges on those islands, their final populations survived on the
slopes and high-elevation reaches of their former ranges
(Fig. 5). These patterns are, of course, entirely consistent with
the contagion hypothesis and the pattern of human coloniza-
tion and development of oceanic islands, which typically
progresses from coastlines, with levels of disturbance and
threat declining in intensity towards the interior and higher-
elevation sites. Again, the geography of extinction and
endangerment is strongly influenced by the dynamic geogra-
phy of human civilizations, our commensals and other
anthropogenic disturbances that transform native ecosystems.
CONCLUSIONS
As with many of Darwin’s insights, the themes discussed here
still have great relevance for understanding the ecological and
evolutionary assembly of isolated biotas, and for conserving
them as well. Although comprising a tremendously diverse
menagerie of novelties and anomalies, each of the marvels of
island life ultimately derive from the special nature of island
ecosystems – their isolated, depauperate and disharmonic
communities – and what I have termed reversals in natural
selection. Ironically, these same selection pressures have
caused these biotas to become ensnared in a myriad of
‘evolutionary traps’. The use of the term in this context dates
back at least to early works of Sewall Wright and Ernst Mayr,
who postulated on both theoretical and empirical grounds
that ‘well-isolated islands are evolutionary traps, which in due
time kill one species after another that settles on them’
(Mayr, 1942, p. 225). Natural selection and inbreeding on
these islands results in their endemic populations ‘…becom-
ing so uniform genetically that they are adapted only to the
particular set of conditions under which they live’ (Mayr,
1942, p. 224; as Wilson, 1965, suggested, this concept is
corollary and derivative to that of faunal dominance, which
he traced back to Darwin, 1859, and subsequent writings of
Matthew, 1915; Simpson, 1953; Darlington, 1957; and Brown,
1957; and it became a central tenet of Wilson’s theory of
taxon cycles; Wilson, 1959, 1961).
200 km
Rinca I.
Flores I.
Komodo I.
Borneo
Java
NewGuinea
Celebes
Flores
Figure 4 Geographic range collapse in the
Komodo dragon (Varanus komodoensis)
exhibits the common pattern of persistence
on true islands and other isolated regions
along the periphery of its former range (his-
torical ranges in dark grey, extant or final
ranges in medium grey). Map produced by R.
Channell, after Sastrawan & Ciofi (2002) (see
also Ciofi & de Boer, 2004).
M. V. Lomolino
990 Journal of Biogeography 37, 985–994ª 2009 Blackwell Publishing Ltd
Over-specialization and extinction were assumed to be the
programmed and inescapable fate of island endemics, but
seldom did evolutionary traps threaten continental biotas.
Some obvious exceptions include episodes of cataclysmic
global change, extinction of the dinosaurs (ectothermic,
inertial homeotherms that were unable to cope with an
asteroid-driven episode of global cooling) and the collapse of
native biotas of long-isolated continents following invasion by
ecologically dominant species (the prototypic case being
expansions of early human civilizations out of Africa). Once
again, selective pressures were reversed, in the latter case
anthropogenically as our ancestors challenged the naıve
endemic biotas (continental and insular) that evolved in
‘splendid isolation’ (sensu Simpson, 1980) and were, thus,
rendered incapable of adapting to what Darwin termed ‘the
strangers’ craft of powers’.
Today’s surviving imperilled species – insular as well as
continental – may again be entangled in a insidious web of
evolutionary traps; reversals in selection pressures (natural and
artificial) of perhaps unparalleled intensity and rapidity –
shifting from those traits associated with adapting to expan-
sive, continuous and diverse continental ecosystems to those
for surviving in or dispersing among artificially insularized
ecosystems (i.e. fragmented and downsized) that are also
ecologically simplified and globally homogenized (due to
repeated introductions of a limited suite of species to most
sites colonized by humans; Lockwood & McKinney, 2001).
Effective conservation thus requires that we strategically
apply the principles inspired by Darwin and generations of
other scientists to gain a more comprehensive understanding
of the ecological and evolutionary assembly (and disassem-
bly) of isolated biotas, including both natural and anthro-
pogenically insularized ones. These and related insights
should enable us not just to conserve the number of species,
but to preserve their natural character as well. This, in turn,
requires that we apply two of the fundamental tenets of a
newly articulated and especially relevant synthesis – conser-
vation biogeography (Lomolino, 2004, 2006; Whittaker et al.,
2005). First, our success in conserving biological diversity
depends heavily on our understanding of the geography of
nature (e.g. what was the historical range of the focal
species, and how did threats to its populations advance
across that range?). Second, but especially important in this
context, is that in order to conserve what Wallace described
as the ‘hugest, and fiercest, and strangest life forms’ and the
true nature of imperilled species (giants, dwarfs and other
marvels of splendid isolation), we need to conserve their
distributions – in so doing, conserving the geographic,
ecological and evolutionary context of nature.
Today’s surviving megafauna may be a poignant case in
point. For example, due to the efforts and support of legions
of dedicated conservation biologists and concerned citizens,
African and Asian elephants may survive for centuries if not
millennia; but in what form? They have been subjected to
many centuries of intense artificial selection, including the
selective take for trophy hunting and the ivory trade, use as
beasts of burden, and culling of captive populations and
those in wildlife reserves – most of these activities selecting
against the largest individuals. Even their ‘wild’ or in situ
populations are becoming increasingly restricted to anthro-
pogenic archipelagos of island-like refugia: relatively small,
isolated and ecologically simplified – often lacking the
Figure 5 Geographic range collapse of insular animals such as Hawaiian birds may appear anomalous compared with the general patterns
for range collapse, but are entirely consistent with the contagion hypothesis – with the final populations persisting in the most isolated
regions of the species former ranges, in this case on the high-elevation reaches of the islands (insets show historical ranges on Kaua’i in black,
extant or final ranges in green). Range maps produced by R. Channell; image of Kaua’i from Google Earth.
Four Darwinian themes
Journal of Biogeography 37, 985–994 991ª 2009 Blackwell Publishing Ltd
natural diversity of large predators and competitors that
may have selected for their mammoth size in the first place.
As implied above, reversals in natural selection may be just
as disruptive for these and many other mainland species that
have become insularized as it was for genuinely insular
biotas following colonization by humans. Elephants may
have been selected for tameness, some of their populations
have become genetically fixed on tusklessness (Jachmann
et al., 1995; Kurt et al., 1995; Whitehouse, 2001; Sukumar,
2003, pp. 292–293), and others appear to be diminished in
their most distinguishing characteristic – their body size. As
Lee & Moss (1995, p. 39) report, ‘elephant heights, at least
in Eastern Africa, have probably declined over the past
100 years…’. Systematic studies of this possible time-dwarf-
ing of Earth’s remaining megafauna, in this case resulting
from selective take and insularization, are sorely needed and
may contribute information essential to the long-term
conservation, not just of the species per se, but of their
natural character as well.
In closing, it is clear that we have much to learn about the
marvels and perils of island life; but it is equally important that
we appreciate and apply the lessons from generations of studies
on insular biotas and, in so doing, honour Charles Darwin and
his singular insights and seminal contributions on the origins,
diversification and preservation of island life.
ACKNOWLEDGEMENTS
I am sincerely grateful to the organizers of this special feature
and the conference – Evolutionary islands: 150 years after
Darwin – and to our gracious hosts at the Museum Naturalis,
Leiden, The Netherlands. Three anonymous referees provided
useful suggestions for improving the manuscript. I also thank
other contributors to this conference for their valued interac-
tion and insights, and for joining our colleagues in paying
homage to Charles Darwin and his enduring contributions to
the natural sciences.
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BIOSKETCH
Mark V. Lomolino’s research and teaching focus on
biogeography and the conservation of biological diversity,
and he is especially interested in processes influencing the
diversity and evolution of isolated faunas, including those of
true islands, as well as those of habitat islands such as nature
reserves, montane forests and fragmented, old-growth forests.
Editor: Menno Schilthuizen
The papers in this Special Issue arose from the symposium
Evolutionary islands: 150 years after Darwin (http://science.nat-
uralis.nl/darwin2009), held from 11 to 13 February 2009 at the
Museum Naturalis, Leiden, The Netherlands. The theme of the
symposium was to explore the contribution of islands to our
understanding of evolutionary biology and to analyse the role
of island biological processes in a world in which the insularity
of island and mainland ecosystems is being drastically altered.
M. V. Lomolino
994 Journal of Biogeography 37, 985–994ª 2009 Blackwell Publishing Ltd