survival in a changing world

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Inside JEB i SURVIVAL IN A CHANGING WORLD In August 2009, the International Union of Physiological Sciences (IUPS) held its 36th Congress in Kyoto in the same convention centre where the historic Kyoto Protocol was drawn up 12 years earlier. The symbolism of this coincidence was not missed by Malcolm Gordon, the Chair of the IUPS’s Commission on Comparative and Environmental and Evolutionary Physiology. For Gordon, a long standing advocate of the importance of ecological and environmental physiology, the meeting in Kyoto was an ideal opportunity to bring together many of the leading voices in the environmental physiology community to look at one of the most pressing issues currently facing the planet: climate change and its ecological and physiological impact. Contacting his IUPS colleague and Editor- in-Chief of The Journal of Experimental Biology Hans Hoppeler, Gordon suggested publishing a collection of review articles addressing the issue of survival in a changing world. Teaming up with Brian Barnes, a leading researcher in Arctic animal physiology, Gordon and Hoppeler have drawn together reviews addressing issues ranging from the impact of climate change on a wide range of terrestrial and aquatic species, to the effects of environmental change on ecosystems and populations, disease distributions and the ability of species to adapt to the environmental changes that they encounter. The opening review by Glen MacDonald discusses the impact of climate change on a major ecological niche; the Arctic (p. 855). With CO 2 levels currently at a 600,000·year high and 100 p.p.m. above previous records, MacDonald warns that future CO 2 levels could reach 500 to 900 p.p.m. by 2100. This coupled with a surface warming pattern unlike any seen before including warmer winters and the phenomenon of Arctic amplification – where northern latitudes warm faster than other regions – leads MacDonald to predict that by the turn of the next century the Arctic ‘will be a brand new world for the plant and animal species of the region’. Reviewing the effects of increased temperatures, relatively warm winters and higher atmospheric CO 2 levels on the growth of the boreal forest and tundra, MacDonald points out that increased temperatures and moisture stress could be major factors in limiting the growth and distributions of some species while increasing that of others. According to MacDonald, the Intergovernmental Panel on Climate Change projections suggest that large areas of tundra could be replaced by boreal forest by as early as 2100. Although the speed of such replacement remains debatable, MacDonald notes that not only would such a displacement impact regional animal populations but also it could ultimately lower the reflectivity of the planet, consequently accelerating climate change. EFFECTS OF CLIMATE AND ENVIRONMENTAL CHANGE ON ECOSYSTEMS Now that the majority of the scientific community has accepted the reality of global climate change, interest has shifted towards assessing the impact that these unprecedented changes are having on populations and ecosystems. Frank La Sorte and Walter Jetz from Yale University describe observed and projected changes in bird distributions in response to climate change and the impact that this is having on their migration strategies and community structures (p. 862). With the huge amount of data that are available on bird distributions, La Sorte and Jetz explain that correlative distribution models (where distribution predictions are based on associations between birds and the climate zones they inhabit) can apply these data to make predictions of the effects that climate change will have on bird populations. However, correlative distribution models are relatively inaccurate, so La Sorte and Jetz propose the development of more sophisticated models that ‘attempt to capture the mechanistic link between species’ distribution and the environment’ to achieve more accurate predictions. While these models will be extremely powerful in the management of well-studied temperate bird populations, La Sorte and Jetz point out that significantly less is known about species in the tropics. The tropics contain approximately 85% of the world’s bird species, and the duo explain that we must find out more about these species as they are at greatest risk from the effects of climate change. Ectothermic creatures, dependent on their environment for thermoregulation, would seem to be even more susceptible to climate change. Ary Hoffmann from The University of Melbourne, Australia, explains that their vulnerability is probably ‘dictated by the proximity of the environment to their physical limits,’ and the ectotherm that he Inside JEB Inside JEB highlights the key developments in The Journal of Experimental Biology. Written by science journalists, the short reports give the inside view of the science in JEB. THE JOURNAL OF EXPERIMENTAL BIOLOGY

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Page 1: SURVIVAL IN A CHANGING WORLD

Inside JEBi

SURVIVAL IN A CHANGINGWORLD

In August 2009, the International Union ofPhysiological Sciences (IUPS) held its 36thCongress in Kyoto in the same conventioncentre where the historic Kyoto Protocolwas drawn up 12 years earlier. Thesymbolism of this coincidence was notmissed by Malcolm Gordon, the Chair ofthe IUPS’s Commission on Comparativeand Environmental and EvolutionaryPhysiology. For Gordon, a long standingadvocate of the importance of ecologicaland environmental physiology, the meetingin Kyoto was an ideal opportunity to bringtogether many of the leading voices in theenvironmental physiology community tolook at one of the most pressing issuescurrently facing the planet: climate changeand its ecological and physiological impact.Contacting his IUPS colleague and Editor-in-Chief of The Journal of ExperimentalBiology Hans Hoppeler, Gordon suggestedpublishing a collection of review articlesaddressing the issue of survival in achanging world. Teaming up with BrianBarnes, a leading researcher in Arcticanimal physiology, Gordon and Hoppelerhave drawn together reviews addressingissues ranging from the impact of climatechange on a wide range of terrestrial andaquatic species, to the effects ofenvironmental change on ecosystems andpopulations, disease distributions and theability of species to adapt to theenvironmental changes that they encounter.

The opening review by Glen MacDonalddiscusses the impact of climate change on amajor ecological niche; the Arctic (p.855).With CO2 levels currently at a 600,000·yearhigh and 100p.p.m. above previous records,MacDonald warns that future CO2 levelscould reach 500 to 900p.p.m. by 2100. Thiscoupled with a surface warming patternunlike any seen before including warmerwinters and the phenomenon of Arcticamplification – where northern latitudeswarm faster than other regions – leadsMacDonald to predict that by the turn ofthe next century the Arctic ‘will be a brandnew world for the plant and animal speciesof the region’. Reviewing the effects ofincreased temperatures, relatively warmwinters and higher atmospheric CO2 levels

on the growth of the boreal forest andtundra, MacDonald points out thatincreased temperatures and moisture stresscould be major factors in limiting thegrowth and distributions of some specieswhile increasing that of others. Accordingto MacDonald, the Intergovernmental Panelon Climate Change projections suggest thatlarge areas of tundra could be replaced byboreal forest by as early as 2100. Althoughthe speed of such replacement remainsdebatable, MacDonald notes that not onlywould such a displacement impact regionalanimal populations but also it couldultimately lower the reflectivity of theplanet, consequently accelerating climatechange.

EFFECTS OF CLIMATE ANDENVIRONMENTAL CHANGE ONECOSYSTEMSNow that the majority of the scientificcommunity has accepted the reality ofglobal climate change, interest has shiftedtowards assessing the impact that theseunprecedented changes are having onpopulations and ecosystems. Frank La Sorteand Walter Jetz from Yale Universitydescribe observed and projected changes inbird distributions in response to climatechange and the impact that this is having ontheir migration strategies and communitystructures (p.862). With the huge amount ofdata that are available on bird distributions,La Sorte and Jetz explain that correlativedistribution models (where distributionpredictions are based on associationsbetween birds and the climate zones theyinhabit) can apply these data to makepredictions of the effects that climatechange will have on bird populations.However, correlative distribution modelsare relatively inaccurate, so La Sorte andJetz propose the development of moresophisticated models that ‘attempt tocapture the mechanistic link betweenspecies’ distribution and the environment’to achieve more accurate predictions. Whilethese models will be extremely powerful inthe management of well-studied temperatebird populations, La Sorte and Jetz pointout that significantly less is known aboutspecies in the tropics. The tropics containapproximately 85% of the world’s birdspecies, and the duo explain that we mustfind out more about these species as theyare at greatest risk from the effects ofclimate change.

Ectothermic creatures, dependent on theirenvironment for thermoregulation, wouldseem to be even more susceptible to climatechange. Ary Hoffmann from The Universityof Melbourne, Australia, explains that theirvulnerability is probably ‘dictated by theproximity of the environment to theirphysical limits,’ and the ectotherm that he

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Inside JEB highlights the keydevelopments in The Journal ofExperimental Biology. Written byscience journalists, the shortreports give the inside view ofthe science in JEB.

THE JOURNAL OF EXPERIMENTAL BIOLOGY

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Inside JEBii

focuses on is the humble fruit fly:Drosophila melanogaster (p.870).According to Hoffmann, species can bevulnerable to environmental change at anumber of levels: the individual, populationor species/lineage. Outlining Drosophila’sability to cope with temperature change andrising aridity through evolution, Hoffmannpoints out that Drosophila hit a ceiling intheir ability to cope with highertemperatures due to their lowheritability/evolvability in response to hightemperatures. However, other Drosophilaspecies seem better able to evolve inresponse to survival in coolingenvironments. Hoffmann is optimistic thattropical species of Drosophila will be nomore threatened by rising temperatures thantemperate species, because their upperthermal thresholds are well above the hightemperature extremes that they mayexperience in the wild.

Moving to the marine domain, Hans-OttoPörtner discusses the effects of climatechange on aquatic ectotherms (p.881).Describing the relationship between tissueoxygen supply and aerobic fitness and theeffect that it has on an organism’s ability tofunction within in an ecosystem, Pörtnerdiscusses the effects of thermal stresscoupled with changing CO2 and O2 levelson water breathing animals. Explaining thataquatic animals, like other organisms, ofnecessity survive within specific thermalwindows, Pörtner adds that this leavesspecies vulnerable to the effects of climatechange, which may bring with ittemperatures outside of an organism’sthermal window. This trend will beexacerbated under hypoxia or elevated CO2levels, both of which can narrow anorganism’s thermal window ofperformance. He emphasizes that we mustbetter understand the relationship betweenenergy turnover, activity capacities and thethermal window to understand how aquaticspecies specialise within a specific nicheand appreciate their vulnerability to climatechange. Pörtner emphasises the importanceof laboratory studies in establishing themechanisms that underlie climate changeeffects on species and provide a linkbetween physiology and ecology to give usa greater understanding of ecosystems at aphysiological level.

One of the most fascinating marineecosystems is the coral reef. Boastingenormous species diversity andunderpinning the economic activities ofmany human populations, these fragileecosystems are some of the most vulnerableon the planet, already exhibiting significantdamage due to environmental degradation.Coral bleaching, ocean acidification andincreased storm frequency are all factors in

the loss of coral reefs. Focusing on the fishcommunities that depend upon and populatecoral reefs, Shaun Wilson, from theDepartment of Environment andConservation, Australia, and a consortiumof 32 collaborators have drawn up a list of53 crucial questions which they feel must beaddressed to ‘advance our understanding ofhow climate change will affect reef fishesand improve the capacity of managers tomitigate such impacts,’ says Wilson (p.894).Almost half of the questions address theissues of habitat associations andcommunity dynamics, while the remainderfocus on expanding our understanding offish physiology, behaviour and management.The consortium hopes that the questionswill guide future research, ultimatelyresulting in better conservation strategies.

While some populations of marine speciesare relatively restricted to a few smallecosystems, loggerhead turtles are truenomads of the sea. However, as largeectotherms, several of the loggerhead’s lifestages are significantly influenced byenvironmental factors, placing them at riskfrom climate change. Annette Broderickand colleagues from the University ofExeter, Bangor University and the NorthCarolina Wildlife Resources Commission,outline the threats posed by increasedtemperatures to loggerhead sex ratios,which are determined by the temperatureof the egg during incubation (p. 901).Concerns about the feminisation of thepopulation due to increased nesttemperatures led Broderick and hercolleagues to call for a betterunderstanding of the influence oftemperature on loggerhead sexdetermination, the identification of nestingsites at risk from high temperatures andthe development of intervention strategiesfor the most vulnerable locations. But itisn’t all bad news for the loggerhead.Broderick acknowledges that temperaturechanges could extend the loggerheads’range north and adds that their broad dietreduces their vulnerability to shifts in preypopulations.

Continuing the theme of climate change onterrestrial and marine populations, George

Somero from the Hopkins Marine Station,California, tackles the question of how anorganism’s ability to acclimatise and adaptgenetically will determine whether itbecomes one of the winners or losers inthe race to survive (p. 912). Focusing onintertidal species, which routinelyexperience extreme thermal stress in theirrocky environment, Somero outlines foursets of questions that address: species’responses to climate change; thephysiological mechanisms that determinean organism’s ability to adapt to a newthermal environment; the issue of whetherprotein evolution can ‘keep pace’ withclimate change; and how an organism’sability to adapt is affected by theregulatory machinery encoded in itsgenome. Having identified that warm-adapted intertidal species are most at riskfrom rising temperatures as they arealready close to their thermal limits,Somero suggests that survival could belimited by cardiac failure at hightemperatures in some species. He adds thatalthough the simple substitution of a singleamino acid can improve the thermalstability of many proteins, the loss ofentire regions of genome essential forsurvival at high temperatures placesAntarctic marine stenotherms at riskshould temperatures in their thermallystable domain begin to rise. Someroconcludes by saying that ‘extremestenotherms, along with warm-adaptedeurytherms living near their thermal limits,may be the major “losers” from climatechange’.

Having discussed the specific effects ofclimate change on a range of species,Tyrone Hayes addresses one of the mostshocking ecological disasters that wecurrently face: the catastrophic loss ofamphibian species, which has been referredto by some as the ‘Earth’s sixth massextinction’. Cataloguing the unprecedenteddecline in amphibian species (p.921),Hayes outlines the main factors that heexplains underpin this phenomenalreduction in biodiversity. Citing climate(atmospheric) change, environmentalpollutants, habitat loss, invasive species andpathogens as the most likely causes of theglobal amphibian decline, Hayessummarises how many of these factorsinteract to reduce amphibian breedingsuccess rates and increase mortality rates.Focusing on the function of pollutants asendocrine disruptors that impactreproduction and act asimmunosuppressants, Hayes warns that‘increased attention to recruitment[reproduction] and ultimate factors [such asenvironmental change] that interact withpathogens are important in addressing thisglobal crisis’.

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DISEASE AND ZOONOSIS INRESPONSE TO CLIMATECHANGEMalcolm Gordon, from the University ofCalifornia Los Angeles, has been intriguedby the effects of disease on animal ecologyfor more than half a century. Gordonremembers debating the issue with one ofthe founders of island biogeography, BobMacArthur, while he was a graduate studentat Yale 50 years ago. ‘We used to discussthe role of disease in terms of animalecology and to what extent diseases wereimportant factors in determining whereanimals occur, how many are there andwhat the densities are,’ remembers Gordon.Recognising the effect of disease at thistime of unprecedented environmentalchange, Gordon invited Laura Mydlarz andher colleagues Elizabeth McGinty andDrew Harvell to review the condition ofcoral reefs and their responses to climatewarming and disease.

Reviewing the disastrous impact of risingtemperatures and emerging diseases oncoral populations (p.934), Mydlarz and hercolleagues state that ‘the crux of both coralsusceptibility and resilience to warming liesin holobiont and symbiont physiologicalresponses to temperature, UV andpathogens’. Defences, such as fluorescentproteins that protect coral animals and theiralgal lodgers from radiation, heat shockresponses and cellular immunity to disease,offer some protection. Mydlarz also pointsout that despite some catastrophic bleachingevents, corals have been able to switch toheterotrophic food intake after losing theiralgal symbionts and have even been able torepopulate their lost algal community withmore thermally robust species. Equippedwith innate immune systems, some coralshave also been able to withstand diseasesthat plague other species. ‘Researchers arefinding indications of resistance andresilience, and in some instances recovery,growth, acclimation and possibleadaptation,’ say Mydlarz and hercolleagues. However, the trio also point outthat 33% of coral species currently facepossible extinction and suspect that ‘it isunlikely that even the compensatory factorsoutlined here will allow for the survival ofintact coral reef systems during upcomingrapid climate changes’.

Climate change is also predicted to impactvector-borne diseases and their episystemsin equally dramatic ways. According toWalter Tabachnick, from the University ofFlorida Medical Entomology Laboratory,vector-borne diseases are extremelysensitive to climate change and he says that‘vector-borne diseases can serve as the“canary in the mine” as a first alert ofchanges due to climate,’ (p.946). However,

predicting changes in disease distributionsand epidemic outbreaks is going to raise asignificant challenge. Outlining the closerelationships between vector-borne diseasesand their environment, Tabachnickdiscusses the effects that climate can haveat various levels in vector-borne diseasesystems. Focusing on two key examples,Bluetongue virus and West Nile virus,Tabachnick emphasizes the complexity ofvector-borne disease episystems. He pointsout that there are many possible causes forthe emergence of either disease in their newlocations, and the role of climate isuncertain. However, since climate is animportant component of these systems, inorder to predict future events, it is essentialthat we better understand the ‘mechanismscontrolling and influencing specificcomponents of the complexvector–pathogen–host cycle,’ saysTabachnick.

Environmental change is not restricted tothe effects of climate. Human encroachmenton pristine territories also results insignificant ecosystem damage throughdeforestation and land degradation. Thedirect impact of deforestation on avianpopulations is well established; however,the indirect effect of landscape change onbird populations through disease is less wellunderstood. Ravinder Sehgal from SanFrancisco State University explains thatbirds harbour and spread several diseasesthat can affect human populations.Discussing the effects of various pathogenson avian populations, Sehgal explains thatthe effects of deforestation are currentlyunclear (p.955). Presenting evidence for theimpact of landscape change on variousdiseases including avian influenza andmalaria, Sehgal says that ‘the impacts ofdeforestation on avian infectious diseaseswill be diverse, and in many cases goundetected,’ but goes on to point out whatwe could learn about the effects ofdeforestation by looking at the effects oflandscape on the diseases of avianpopulations.

Concluding the section on the interactionbetween environmental change and disease,Pieter Johnson from the University ofColorado, USA, and David Thieltges from

the University of Otago, New Zealand,discuss how the loss of biodiversity canpromote increases in disease withincommunities (p. 961). According toJohnson, species-rich communities canpotentially snuff out transmission ofpathogens, such as parasites, by ‘wasted’transmissions to hosts who are unable topass the parasite on to the next life stage.Listing diseases that thrive in communitieswith low biodiversity, ranging frommalformation in frogs to schistosomiasis inhumans, Johnson outlines the mechanismsthat reduce disease transmission in species-rich communities and lists factors that mustbe considered when assessing thelikelihood that a community will exhibitsuch a ‘disease dilution’ effect. Johnsonconcludes by saying that ‘we are onlybeginning to understand the importance ofdiversity in complex disease systems,’ butadds that ‘the rapid decline of manypopulations and species coupled with anincrease in species invasions can beexpected to have ramifications for diseasedynamics’.

ANIMAL RESILIENCE,ADAPTATION ANDPREDICTIONS FOR COPINGWITH CHANGEWhile resilience, the ability to respond tochange, is a well understood ecologicalconcept, Brian Barnes from The Universityof Alaska Fairbanks explains his owninterest is in the physiological responsesthat underpin resilience. ‘Resilience isn’tstasis,’ he explains, ‘but where you can endup in a place where you can still maintainhomeostatic relationships and functionalsystems but they may be different.’ Giventhe changes that many species are alreadyencountering, resilience will be a key factorthat will allow them to adapt to rapidlychanging environmental conditions.

Ectothermic species that survive in theintertidal zone experience some of the mostextreme diurnal body temperature ranges onthe planet. Lars Tomanek from CaliforniaPolytechnic State University, USA, explainsthat intertidal species can experience andsurvive daily rises in body temperature of20°C: 4 times the most extreme humanfever. Many of these thermally tolerantspecies owe their survival to a systemknown as the heat shock response, whichprotects proteins and cells from damage athigh temperatures. However, many animalsin regions that have been thermally stablefor thousands of years, such as the polaroceans, appear to have lost these heat shockresponses and would seem to be morevulnerable to climate change than theirintertidal relatives. Curious to find outwhich marine invertebrates will be mostvulnerable to rising global temperatures,

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Tomanek reviews the literature (p.971) andfinds that even though intertidal specieshave a well established heat shock responsethey are as vulnerable to climate change aspolar species, because intertidal populationslive close to their thermal limit and areunable to mount a heat shock response totemperatures higher than their currentmaximal body temperatures. In contrast,subtidal species that survive in moremoderate thermal environments are able toproduce a heat shock response whenexposed to higher temperatures and so areless vulnerable to climate change.

Moving from marine invertebrates toinsects, Jeff Bale from The University ofBirmingham, UK, explains that while it isconvenient to classify overwintering insectsas either freeze tolerant or freeze avoiding,in reality the great majority of insects arekilled by cold not freezing. So how willoverwintering insects be affected as wintertemperatures rise? Bale predicts thattemperature rises between 1 and 5°C willlead to increased insect survival (p.980);however, he adds that this effect is‘unlikely to be universal’. Explaining thatpolar insects are currently protected fromlethally low temperatures by snow cover,Bale predicts that these species couldbecome more vulnerable as temperaturesrise and snow cover is lost. Highertemperatures could also impact insectdevelopmental rates, causing theprogression of critical life stages to becomeunsynchronised from the day length signalthat usually triggers the transition to asubsequent life stage. Bale adds that someregions will become too hot for insects tosurvive and concludes that while a rise inglobal temperatures will be unharmful, oreven beneficial, for the majority of insectspecies, the impact of higher temperaturesmay be profound for polar and tropicalspecies.

Having discussed how species mayrespond to alterations in the climate, it isalso essential that scientists make accuratepredictions of areas that may be under themost extreme threat from climate change.Brian Helmuth from the University ofSouth Carolina explains that the factors,such as body temperature, that directlyaffect an organism’s physiologicalresponse, may bare little relation to theenvironmental air temperature. Returningto the intertidal zone, Helmuth andcolleagues explain that the bodytemperature of a mussel is dependent on awide range of local factors, such as themollusc’s orientation to the sun, the extentof cloud cover and wind speed. Focusingon the ‘climatology’ of body temperatures,Helmuth describes how he has collectedbody temperature data on the organismalscale with ‘robomussel’ data loggers inPacific Grove, California, every 10·minsince 2000 (p. 995). Describing howdramatically the robomussel’s ‘body’temperature differs from the environmental(e.g. air) temperature, Helmuth says, ‘theseresults strongly suggest that estimates ofstress in the field need to be derived fromniche-level measurements or modelsrelevant to physiological performance suchas temperature’. Helmuth concludes bysaying that ‘forecasting the location,magnitude and timing of the impacts ofclimate change on ecosystems is a

critically important task,’ and is optimisticthat his approach to measuring theclimatology of body temperatures couldimprove our prediction of catastrophicevents.

SURVIVAL IN A CHANGINGWORLD: THE FUTUREWith the failure of the Copenhagensummit to draft a legally bindingagreement on the reduction of global CO2emission rates, it seems almost certainthat we will see further rapid changes inthe global climate. But, as far as MalcolmGordon is concerned, ‘the argument aboutwhether the change in climate is theresult of human activity or some othernatural changes is of little relevance asfar as the subject of this special issue isconcerned. The changes are happeningand they are affecting everything – plants,animals, entire ecosystems – and thechanges will also affect the climate of theatmosphere and the oceanic climate andcurrent distributions’. Gordon goes on topoint out that environmental physiologistshave never been better poised toinfluence global conservation policy.Documenting the consequences ofenvironmental change and themechanisms that will allow some speciesto adapt, while leaving others vulnerableto extinction, it is clear thatenvironmental physiologists will have apivotal role in guiding the globalresponse to climate change. Ultimately,Gordon and Barnes are optimistic thatthis collection of reviews will help inspirethe next generation of environmentalphysiologists to address these challenges,raise awareness and begin influencingglobal environmental policy.10.1242/jeb.043364

Kathryn [email protected]

© 2010. Published by The Company of Biologists Ltd

THE JOURNAL OF EXPERIMENTAL BIOLOGY