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: island@esf.edu

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