Four Darwinian Themes on the Origin, Evolution and Preservation of Island

Journal of Biogeography (J. Biogeogr.) (2010) 37, 985–994

SPECIAL Four Darwinian themes on the origin, ISSUE evolution and preservation of island life Mark V. Lomolino*

College of Environmental Science and Forestry, ABSTRACT Syracuse, NY 13210, USA 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). *Correspondence: Mark V. Lomolino, College of Keywords Environmental Science and Forestry, Syracuse, NY 13210, USA. Assembly, biogeography, Charles Darwin, conservation, evolution, extinction, E-mail: [email protected] islands.

‘As with shipwrecked mariners near a coast, it would have been on the decline of nature over a century before ‘biodiversity’ better for the good swimmers if they had been able to swim still and ‘conservation biology’ were first articulated. further,…’ Here I provide an historical and prospective overview of the ‘A gun is here almost superfluous...’ development of theory on the ecological and evolutionary ‘It is impossible to reflect on the changed state of the American assembly of insular biotas and, in particular, the continuing continent without the deepest astonishment.’ capacity of island studies to provide fundamental insights for ‘Humboldt saw in South America a parrot which was the sole living conserving the diversity and natural character of native biotas. creature that could speak a word of the language of a lost tribe…’ 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 INTRODUCTION prospect that the tables should now be turned; that our The above excerpts of quotations from Charles Darwin’s abilities to predict and hopefully mitigate the effects of writings, which I present and discuss in detail below, capture artificial selection incurred through species introductions, themes that proved seminal for generations of scientists who overharvesting and anthropogenic insularization (via habitat were equally captivated by both the marvels and the perils of loss and fragmentation) rest heavily on the revelations of island life. Although presented as I have done so above as Darwin and generations of countless others who studied the disarticulated and seemingly unrelated metaphors and observa- effects of natural selection on isolated biotas. The relevance of tions, these passages from Darwin’s publications serve as mile island studies is only likely to increase as their native biotas markers along a professional and personal journey shared by become ever rarer, and as an increasing proportion of most scientists who study island life: one that progresses from an continental biotas become more restricted to island-like innate attraction for insular biotas, to an astonishment over their ecosystems (e.g. wildlife parks, nature reserves and other rem- distinct and seemingly bizarre character, a quest to explain these nants of once expansive and continuous, native ecosystems). phenomena in the most fundamental terms, and finally to a My purpose here is to discuss four themes inspired by the sobering understanding of the fragility of island life and of our research and writings of Charles Darwin; themes on the obligations as scientists and the planet’s only global stewards to assembly (and disassembly) of insular biotas which continue to conserve these imperilled biotas. hold great promise for providing insights into their ecological Darwin, of course, was not the first naturalist to study the and evolutionary development, and for conserving the natural diversity and singular nature of island life, but his classic works character and evolutionary potential of species restricted to clearly constitute a seminal nexus in the reticulating phylogeny isolated ecosystems (natural or anthropogenic). The first of island theory. Perhaps just as important, Darwin remarked theme describes how selective pressures on islands are often

ª 2009 Blackwell Publishing Ltd www.blackwellpublishing.com/jbi 985 doi:10.1111/j.1365-2699.2009.02247.x M. V. Lomolino reversed from those in species-rich, taxonomically balanced ‘As Professor Owens has remarked, there is no greater anomaly in communities of the continents. The second and third themes nature than a bird that cannot fly.’ address resultant effects of those reversals in selection forces, (Darwin, 1859, pp. 175–176) ¨ ´ including the development of naıvete and the fragility of The anomaly, however, was rendered explicable by Darwin’s insular biotas, and the downsizing (through megafaunal eloquent metaphor of shipwrecked mariners. The natural extinctions) and evolutionary convergence on phenotypes that ontogeny of island endemics is one of regular and highly are optimal in species-poor and disharmonic communities of predictable reversals in natural selection from that for the ‘good remote, oceanic islands. The final theme addresses the swimmers’ during immigration, to selection for those adapted to geography of extinction which, seemingly paradoxically to the special nature of insular environments following coloniza- the general fragility of insular biotas, is characterized by tion. Many hundreds of birds, insects and plants – in succumb- persistence of the most isolated populations. ing to the pressures for ‘sticking to the wreck’ – ultimately lost Most examples and case studies that I discuss here are of the capacity to disperse to other islands (see McNab, 1994). terrestrial systems, especially vertebrates. I leave it to others to explore the heuristic and applied relevance of these themes to other ecosystems and taxa. 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.’ FOUR DARWINIAN THEMES ON THE ASSEMBLY (Darwin, 1860, Ch. 17, Galapagos Archipelago) OF INSULAR BIOTAS Reversals in natural selection are at the heart of explanations Theme 1. Reversals in natural selection: from for not only the many marvels of island life, but its fragility as ‘swimming’ to ‘sticking to the wreck’ well. That is, selection for adaptation to the special nature of ‘As with shipwrecked mariners near a coast, it would have been insular environments – which include not just their isolation better for the good swimmers if they had been able to swim still and limited area, but the depauperate and disharmonic nature further, whereas it would have been better for the bad swimmers if of their communities – results in fundamental transformations they had not been able to swim at all and had stuck to the wreck.’ in the character of insular species. In addition to the striking (Darwin, 1859, p. 177) anomalies of flightless birds and insects discussed by Darwin I begin with the above passage from The Origin because it and many others, these transformations include a suite of provides a conceptual framework fundamental to understand- equally remarkable reversals in morphology, physiology and ing the ecological and evolutionary assembly of island life: behaviour in countless other species – ecological and evolu- reversals in selective pressures which produce both the marvels tionary adaptations of insular species to remote island and perils of island life. Darwin used the first part of this communities, which are typically free of terrestrial mammals. metaphor to explain a type of natural selection quite different Under these conditions, both plants and animals often lose the from ‘survival of the fittest’. That is, he envisioned this form of structures and behaviours essential for predator (carnivore and natural selection occurring during immigration to very isolated herbivore) avoidance on the mainland (Carlquist, 1965, 1974; islands, and resulting in founding populations biased in favour Lomolino et al., 2006; Whittaker & Fernańdez-Palacios, 2007). of individuals with superior immigration abilities. Unlike drift On the mainland, interspecific interactions in species-rich and random founding effects, immigrant selection (sometimes and ecologically balanced communities can drive ecological termed ‘selection for thrifty genotypes’ by anthropologists; and evolutionary divergence among species; some plants Neel, 1962) can explain directional trends in the structure of avoiding competition and herbivory by dispersing to colonize insular communities and populations (e.g. towards dishar- ephemeral habitats and growing and reproducing rapidly (as mony and dominance of particular, highly vagile species or herbaceous forms), others investing more in arsenals of thorns phenotypes: see Darlington, 1957; Carlquist, 1966a,b; Lomo- and defensive chemicals. In animals, divergence in body size on lino, 1984, 1993; and Bindon & Baker, 1997). the continents may be in response to selective pressures to Of even more fundamental importance in terms of under- reduced competition or escape predators; e.g. some species standing the special nature of insular biotas is the second part decreasing in size and thus becoming more capable of finding of Darwin’s metaphor because it cogently asserts that selective shelter in burrows or under rocks and logs; others increasing in pressures vary – but in a very predictable manner – both size and simply outgrowing their would-be predators; and still among species and across the stages of ecological and others reducing predation risks by becoming more vigilant, evolutionary assembly of insular biotas. Indeed, Darwin was more swift of foot or, in the case of bats and birds, true fliers. using the above metaphor to explain some intriguing reversals, On islands, however, interspecific interactions and associated paradoxes and anomalies of island life, including the many selective pressures are dramatically reduced – shifting towards reports from archaeologists and neo-naturalists such as Sir those associated with more intense competition from conspe- Richard Owen, who described endemic birds of remote cifics and a very limited and disharmonic group of other oceanic islands such as dodos, moas and elephant birds that insular residents (dominated by the biota of long-distance totally lacked the power of flight. dispersal and their descendants).

986 Journal of Biogeography 37, 985–994 ª 2009 Blackwell Publishing Ltd Four Darwinian themes

In his account of the voyage of the Beagle, Darwin described the naı¨vete´ 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.’ Figure 2 The rise in extinction rates of continental animals (in ‘We may infer from these facts, what havoc the introduction of any particular, mammals, molluscs and birds) relative to those on new beast of prey must cause in a country, before the instincts of the indigenous inhabitants have become adapted to the stranger’s craft oceanic islands over the most recent decades may again be insular of power.’ in nature, as once expansive continental systems have been insu- (Darwin, 1860, Ch. 17, Galapagos Archipelago) larized by habitat conversion and expansion of anthropogenic ecosystems (from Lomolino et al., 2006; after World Conservation The fragility of island life is all too well documented in the Monitoring Centre, 1992). 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 observed that nature was in decline, much of it for the same species (including humans) who devastated native insular biotas reasons outlined above – artificial (anthropogenic) selection, before they could adapt to what Darwin described as the including species introductions, conversions of native habitats, ‘stranger’s craft of power’. Even in more recent times, when the and over-harvesting. Thus, in 1839 he observed that: rate of extinctions on the continents now rivals that of islands ‘It is impossible to reflect on the changed state of the American (Fig. 2), extinctions may again be insular in nature; in this case continent without the deepest astonishment. Formerly it must have because invading human civilizations and technologies have swarmed with great monsters: now we find mere pigmies, compared converted once expansive continental landscapes to archipelagos with the antecedent, allied races.’ (Darwin, 1839, p. 448) of remnant habitats isolated within seas of anthropogenic ecosystems (see also Ellis & Ramankutty, 2008). 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 Theme 3. Megafaunal extinctions and body size principle of reversals in natural selection, but this time convergence referring to its effects on continental biotas during prehistoric Well before conservation biology became an established periods (i.e. during aboriginal colonization of the New World discipline, and perhaps over a century before the term and subsequent collapse of its megafauna): ‘biodiversity’ was coined, Darwin and his contemporaries ‘… 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- Figure 1 The fragility of island life is clearly evidenced in the tal biotas (a pattern so fundamental to biogeography that disproportionate number of extinctions of insular vs. continental it eventually became known as Buffon’s law) results from plants and animals over the past 500 years (from Lomolino et al., divergence in isolation, with some forms advancing or being 2006; after Reid & Miller, 1989). amplified while others degenerate in response to conditions of

Journal of Biogeography 37, 985–994 987 ª 2009 Blackwell Publishing Ltd M. V. Lomolino their environments (i.e. those of the New World). As we know On isolated, small or otherwise depauperate islands, the today, palaeontologists have uncovered irrefutable evidence in mammals and other terrestrial vertebrates that do persist tend to favour of Darwin’s views: the long-isolated continents of the exhibit a pattern of evolutionary convergence termed the island New World, along with Australia and large islands, were in the rule, with small species increasing in size and large (including not-so-distant past inhabited by their own megafauna, in megafaunal) species decreasing in size (Fig. 3a; see Lomolino, many cases rivalling that of vertebrate assemblages still 1985, 2005). The pattern is quite general and, despite much persisting in Africa and other regions of the Old World variation within and among various groups of mammals, most tropics. Not surprisingly, Alfred Russel Wallace’s views on this exhibit the trend of convergence towards an intermediate body point were entirely consistent with those of Darwin: size (Fig. 3b; but see Meiri et al., 2004; and Meiri, 2007). The pattern is reported for other terrestrial vertebrates, including ‘We live in a zoologically impoverished world, from which all the insular birds (Clegg & Owens, 2002) and reptiles (Boback, 2003; hugest, and fiercest, and strangest forms have recently disappeared.’ (Wallace, 1876, p. 150) Boback & Guyer, 2003; but see Meiri, 2007, 2008, and Hedges, 2008), and for marine gastropods inhabiting isolated regions of These episodes of megafaunal collapse provide additional the deep sea (McClain et al., 2006) and nine-spined sticklebacks evidence for the importance of anthropogenic reversals in (Pungitius pungitius) inhabiting small ponds lacking their key selective forces; in this case from those prevailing throughout predators (Herczeg et al., 2009). This phenomenon also appears much of the late Cenozoic – which favoured the formation of to be ancient – being exhibited in insular mammals during ‘large germs’, to the reversals that caused their extinctions during Pliocene to Holocene times (Fig. 3b; for a possible example in the latter stages of the Pleistocene. These megafaunal extinctions insular hominids see Brown et al., 2004, and Morwood et al., were probably the result of repeated range expansions and 2004) and possibly in insular sauropods as well (Jianu & colonization by ecologically significant humans and subsequent Weishampel, 1999; Sander et al., 2006). artificial selection against the giants and other marvels of A related phenomenon and response to the depauperate and evolution in isolation (see Flannery, 1994; Grayson & Meltzer, disharmonic nature of remote islands is ecological and 2003; Barnosky et al., 2004; Martin, 2005; Gillespie, 2008). The evolutionary release in the form of ‘super-generalists’ (sensu ultimate results of colonizations by exotic, human civilizations Olesen et al., 2002). On remote, species-poor islands, some of were entire assemblages that have been downsized through the inhabitants may increase their niche breadths and symbi- species selection (i.e. the loss of their largest species), and otic capacities to adapt and interact (e.g. as generalist possibly through microevolutionary downsizing of surviving pollinators and seed dispersers) with a relatively high number forms as well. Flannery (1994) has termed this latter process of species in comparison to their mainland ancestors. As ‘time-dwarfing’, and he provides some intriguing putative Olesen & Valido (2003) have shown, super-generalists on examples. Following the colonization of Australia by aborigines islands often include lizards, which rarely serve as pollinators some 55,000 to 60,000 years bp, all the mega-marsupials greater and dispersal agents on the mainland. For example, of the than 400 kg suffered extinction, while all those smaller than 5 kg world’s lizard species, some 95% of those known to visit were apparently spared. Many of those of intermediate size did flowers (and presumably serve as pollinators) and 63% of survive, but in altered form with the most pronounced cases of those known to feed on fruit (dispersing their seeds) time-dwarfing occurring in the largest surviving species (the are insular forms. These interrelated island phenomena – of body mass of red and grey kangaroos decreasing by about 30%, super-generalists and unusual pollinators and dispersal agents, while that of much smaller species such as spotted quolls and probably result from density overcompensation of lizard rock wallabies declined by less than 10%; see Flannery, 1994, pp. populations and lower predation risks, both of these associated 208–216; and Lomolino et al., 2006, p. 559; but see Price, 2008). with the absence or paucity of non-volant mammals, selected These patterns in species selection and body size evolution arthropods and other competitors, pollinators and predators of the surviving megafauna on the island continent of Australia on remote islands. are similar to those reported for many vertebrates on true One very important lesson from these case studies in the islands. Just as for continental biotas, the list of the world’s ecological and evolutionary assembly of insular biotas is that extinct and endangered insular species comprises a dispropor- reversals in natural selection, whether natural or anthropo- tionate number of large animals including megafaunal tor- genic, can fundamentally transform both the diversity and the toises, snakes and lizards, along with many species of large, natural character of native biotas. flightless birds [e.g. the dodo (Raphus cucullatus) of Mauritius, the solitaires (Raphus solitarius and Pezophaps solitariaon)of Theme 4. Humboldt’s parrot: the geography of Reúnion and Rodriguez, the elephant birds (Aepyornithidae) extinction in man and beasts of Madagascar and the moas (Pachyornis spp.) of New Zealand]. The collapse of New Zealand’s 10 to 15 species of Perhaps one of the most surprising if not astounding of moas is an exemplary case of size-selective extinctions, with the Darwin’s observations discussed here is his reference to one sequence of extinctions generally progressing from the largest of Alexander von Humboldt’s discoveries. Although seem- to smallest species following colonization of the islands by the ingly an aside to Humboldt’s more broadly recognized and Maori people (Worthy & Holdaway, 2002). seminal contributions (see Jackson, 2009), he describes a

988 Journal of Biogeography 37, 985–994 ª 2009 Blackwell Publishing Ltd Four Darwinian themes

(a)

(b)

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).

Journal of Biogeography 37, 985–994 989 ª 2009 Blackwell Publishing Ltd M. V. Lomolino

Celebes Borneo New Guinea

Flores Java

Komodo I.

Flores I. Figure 4 Geographic range collapse in the Komodo dragon (Varanus komodoensis) exhibits the common pattern of persistence Rinca I. on true islands and other isolated regions along the periphery of its former range (historical ranges in dark grey, extant or final ranges in medium grey). Map produced by R. 200 km Channell, after Sastrawan & Ciofi (2002) (see also Ciofi & de Boer, 2004). phenomenon that is identical in most respects to patterns the contagion hypothesis and the pattern of human coloniza- only recently emerging from modern studies on the geogra- tion and development of oceanic islands, which typically phy of extinction. progresses from coastlines, with levels of disturbance and threat declining in intensity towards the interior and higher- ‘Humboldt saw in South America a parrot which was the sole living elevation sites. Again, the geography of extinction and creature that could speak a word of the language of a lost tribe. Ancient monuments and stone implements found in all parts of the endangerment is strongly influenced by the dynamic geogra- world, of which no tradition is preserved by the present inhabitants, phy of human civilizations, our commensals and other indicate much extinction. Some small broken tribes, remnants of anthropogenic disturbances that transform native ecosystems. former races, still survive in isolated and generally mountainous districts.’ [bold added here for emphasis] (Darwin, 1871, p. 252) CONCLUSIONS

Beyond the truly remarkable preservation in the grey matter As with many of Darwin’s insights, the themes discussed here of a parrot of approximately 40 cognate phrases of this now still have great relevance for understanding the ecological and extinct culture, Darwin’s account accurately describes geo- evolutionary assembly of isolated biotas, and for conserving graphic range collapse, not just in other human populations them as well. Although comprising a tremendously diverse such as the Incas and Anasazi, but across a broad diversity of menagerie of novelties and anomalies, each of the marvels of other species as well (Lomolino & Channell, 1995; Channell & island life ultimately derive from the special nature of island Lomolino, 2000; Gaston, 2003; Laliberte & Ripple, 2004). The ecosystems – their isolated, depauperate and disharmonic final refugia of collapsing biotas tend to be located along the communities – and what I have termed reversals in natural most isolated reaches of their historical geographic range: selection. Ironically, these same selection pressures have along its periphery, on mountaintops, or islands (Fig. 4). caused these biotas to become ensnared in a myriad of These are the last sites to be contacted and eventually ‘evolutionary traps’. The use of the term in this context dates overwhelmed by extinction forces, which spread like a back at least to early works of Sewall Wright and Ernst Mayr, contagion across native landscapes and seascapes. As a result, who postulated on both theoretical and empirical grounds many of the once broadly distributed but now imperilled that ‘well-isolated islands are evolutionary traps, which in due continental species have become insularized: restricted to time kill one species after another that settles on them’ anthropogenic archipelagos of remnant habitats, isolated from (Mayr, 1942, p. 225). Natural selection and inbreeding on other remnant populations and restricted to geographically these islands results in their endemic populations ‘…becom- limited and ecologically simplified ecosystems. ing so uniform genetically that they are adapted only to the Patterns of geographic range collapse for exclusively insular particular set of conditions under which they live’ (Mayr, species, such as Hawaiian birds, plants and snails, represent 1942, p. 224; as Wilson, 1965, suggested, this concept is apparently anomalous but especially instructive case studies. corollary and derivative to that of faunal dominance, which Rather than persisting along the periphery of the species’ he traced back to Darwin, 1859, and subsequent writings of ranges on those islands, their final populations survived on the Matthew, 1915; Simpson, 1953; Darlington, 1957; and Brown, slopes and high-elevation reaches of their former ranges 1957; and it became a central tenet of Wilson’s theory of (Fig. 5). These patterns are, of course, entirely consistent with taxon cycles; Wilson, 1959, 1961).

990 Journal of Biogeography 37, 985–994 ª 2009 Blackwell Publishing Ltd Four Darwinian themes

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.

Over-specialization and extinction were assumed to be the bly) of isolated biotas, including both natural and anthro- programmed and inescapable fate of island endemics, but pogenically insularized ones. These and related insights seldom did evolutionary traps threaten continental biotas. should enable us not just to conserve the number of species, Some obvious exceptions include episodes of cataclysmic but to preserve their natural character as well. This, in turn, global change, extinction of the dinosaurs (ectothermic, requires that we apply two of the fundamental tenets of a inertial homeotherms that were unable to cope with an newly articulated and especially relevant synthesis – conser- asteroid-driven episode of global cooling) and the collapse of vation biogeography (Lomolino, 2004, 2006; Whittaker et al., native biotas of long-isolated continents following invasion by 2005). First, our success in conserving biological diversity ecologically dominant species (the prototypic case being depends heavily on our understanding of the geography of expansions of early human civilizations out of Africa). Once nature (e.g. what was the historical range of the focal again, selective pressures were reversed, in the latter case species, and how did threats to its populations advance anthropogenically as our ancestors challenged the naı¨ve across that range?). Second, but especially important in this endemic biotas (continental and insular) that evolved in context, is that in order to conserve what Wallace described ‘splendid isolation’ (sensu Simpson, 1980) and were, thus, as the ‘hugest, and fiercest, and strangest life forms’ and the rendered incapable of adapting to what Darwin termed ‘the true nature of imperilled species (giants, dwarfs and other strangers’ craft of powers’. marvels of splendid isolation), we need to conserve their Today’s surviving imperilled species – insular as well as distributions – in so doing, conserving the geographic, continental – may again be entangled in a insidious web of ecological and evolutionary context of nature. evolutionary traps; reversals in selection pressures (natural and Today’s surviving megafauna may be a poignant case in artificial) of perhaps unparalleled intensity and rapidity – point. For example, due to the efforts and support of legions shifting from those traits associated with adapting to expan- of dedicated conservation biologists and concerned citizens, sive, continuous and diverse continental ecosystems to those African and Asian elephants may survive for centuries if not for surviving in or dispersing among artificially insularized millennia; but in what form? They have been subjected to ecosystems (i.e. fragmented and downsized) that are also many centuries of intense artificial selection, including the ecologically simplified and globally homogenized (due to selective take for trophy hunting and the ivory trade, use as repeated introductions of a limited suite of species to most beasts of burden, and culling of captive populations and sites colonized by humans; Lockwood & McKinney, 2001). those in wildlife reserves – most of these activities selecting Effective conservation thus requires that we strategically against the largest individuals. Even their ‘wild’ or in situ apply the principles inspired by Darwin and generations of populations are becoming increasingly restricted to anthro- other scientists to gain a more comprehensive understanding pogenic archipelagos of island-like refugia: relatively small, of the ecological and evolutionary assembly (and disassem- isolated and ecologically simplified – often lacking the

Journal of Biogeography 37, 985–994 991 ª 2009 Blackwell Publishing Ltd M. V. Lomolino natural diversity of large predators and competitors that Buffon, G.L.L., Comte de (1766) Histoire naturelle, geńe´rale et may have selected for their mammoth size in the first place. particulie`re. Vol. 5. Imprimerie Royale, Paris. [Translated As implied above, reversals in natural selection may be just into English by W. Smellie (1781), London.] as disruptive for these and many other mainland species that Carlquist, S. (1965) Island life. Natural History Press, Garden have become insularized as it was for genuinely insular City, NY. biotas following colonization by humans. Elephants may Carlquist, S. (1966a) The biota of long-distance dispersal. I. have been selected for tameness, some of their populations Principles of dispersal and evolution. Quarterly Review of have become genetically fixed on tusklessness (Jachmann Biology, 41, 247–270. et al., 1995; Kurt et al., 1995; Whitehouse, 2001; Sukumar, Carlquist, S. (1966b) The biota of long-distance dispersal. II. Loss 2003, pp. 292–293), and others appear to be diminished in of dispersibility in Pacific Compositae. Evolution, 20, 30–48. their most distinguishing characteristic – their body size. As Carlquist, S. (1974) Island biology. Columbia University Press, Lee & Moss (1995, p. 39) report, ‘elephant heights, at least New York. in Eastern Africa, have probably declined over the past Channell, R. & Lomolino, M.V. (2000) Dynamic biogeography 100 years…’. Systematic studies of this possible time-dwarf- and conservation of endangered species. Nature, 403, 84–86. ing of Earth’s remaining megafauna, in this case resulting Ciofi, C. & de Boer, M. (2004) Distribution and conservation from selective take and insularization, are sorely needed and of the Komodo monitor Varanus komodoensis. Herpetologi- may contribute information essential to the long-term cal Journal, 14, 99–107. conservation, not just of the species per se, but of their Clegg, S.M. & Owens, I.P.F. (2002) The ‘island rule’ in birds: natural character as well. medium body size and its ecological explanation. Proceedings In closing, it is clear that we have much to learn about the of the Royal Society B: Biological Sciences, 269, 1359–1365. marvels and perils of island life; but it is equally important that Darlington, P.J., Jr (1957) Zoogeography: the geographical dis- we appreciate and apply the lessons from generations of studies tribution of animals. John Wiley and Sons, New York. on insular biotas and, in so doing, honour Charles Darwin and Darwin, C. (1839) Journal of the researches into the geology and his singular insights and seminal contributions on the origins, natural history of various countries visited by H.M.S. Beagle, diversification and preservation of island life. under the command of Captain Fitzroy, R.N. from 1832 to 1836. Henry Colburn, London. Darwin, C. (1859) The origin of species by means of natural ACKNOWLEDGEMENTS selection or the preservation of favoured races in the struggle I am sincerely grateful to the organizers of this special feature for life. John Murray, London. and the conference – Evolutionary islands: 150 years after Darwin, C. (1860) Journal of researches into the natural history Darwin – and to our gracious hosts at the Museum Naturalis, and geology of the countries visited during the voyage of Leiden, The Netherlands. Three anonymous referees provided H.M.S. Beagle round the world. 10th thousand. John Murray, useful suggestions for improving the manuscript. 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Journal of Biogeography 37, 985–994 993 ª 2009 Blackwell Publishing Ltd M. V. Lomolino

Whittaker, R.J. & Ferna´ndez-Palacios, J.M. (2007) Island BIOSKETCH biogeography: ecology, evolution and conservation, 2nd edn. Oxford University Press, Oxford. Mark V. Lomolino’s research and teaching focus on Whittaker, R.J., Arau´ jo, M.B., Jepson, P., Ladle, R.J., Watson, biogeography and the conservation of biological diversity, J.E.M. & Willis, K.J. (2005) Conservation Biogeography: and he is especially interested in processes inﬂuencing the assessment and prospect. Diversity and Distributions, 11, 3–23. diversity and evolution of isolated faunas, including those of Wilson, E.O. (1959) Adaptive shift and dispersal in a tropical true islands, as well as those of habitat islands such as nature ant fauna. Evolution, 13, 122–144. reserves, montane forests and fragmented, old-growth forests. Wilson, E.O. (1961) The nature of the taxon cycle in the Melanesian ant fauna. The American Naturalist, 95, 169– 193. Editor: Menno Schilthuizen Wilson, E.O. (1965) The challenge from related species. The genetics of colonizing species (ed. by H.G. Baker and G.L. The papers in this Special Issue arose from the symposium Stebbins), pp. 7–24. Academic Press, New York. Evolutionary islands: 150 years after Darwin (http://science.nat- World Conservation Monitoring Centre (1992) Global biodi- uralis.nl/darwin2009), held from 11 to 13 February 2009 at the versity: status of the Earth’s living resources. Chapman & Hall, Museum Naturalis, Leiden, The Netherlands. The theme of the New York. symposium was to explore the contribution of islands to our Worthy, T.H. & Holdaway, R.N. (2002) The lost world of the understanding of evolutionary biology and to analyse the role moa: prehistoric life of New Zealand. Indiana University of island biological processes in a world in which the insularity Press, Bloomington. of island and mainland ecosystems is being drastically altered.

994 Journal of Biogeography 37, 985–994 ª 2009 Blackwell Publishing Ltd