Acclimation to predicted ocean warming through developmental plasticity in a tropical reef fish

Determining the capacity of organisms to acclimate and adapt to increased temperatures is key to understand how populations and communities will respond to global warming. Although there is evidence that elevated water temperature affects metabolism, growth and condition of tropical marine fish, it is unknown whether they have the potential to acclimate, given adequate time. We reared the tropical reef fish Acanthochromis polyacanthus through its entire life cycle at present day and elevated (+1.5 and+3.0 °C) water temperatures to test its ability to thermally acclimate to ocean temperatures predicted to occur over the next 50–100 years. Fish reared at 3.0 °C greater than the present day average reduced their resting oxygen consumption (RMR) during summer compared with fish reared at present day temperatures and tested at the elevated temperature. The reduction in RMR of up to 69 mg O₂ kg^?1 h^?1 in acclimated fish could represent a significant benefit to daily energy expenditure. In contrast, there was no acclimation to summer temperatures exhibited by fish reared at 1.5 °C above present day temperatures. Fish acclimated to +3.0 °C were smaller and in poorer condition than fish reared at present day temperatures, suggesting that even with acclimation there will be significant consequences for future populations of tropical fishes caused by global warming.     

The interactive effects of photoperiod and future climate change may have negative consequences for a wide‐spread invasive insect

Increasing global temperatures may affect many ectotherms, including insects, although increasing temperatures are thought to benefit future populations through effects on adult size, fecundity, or populations. However, the way that temperature may interact with photoperiod is not well understood. We study this problem using the Asian tiger mosquito Aedes albopictus, an important worldwide invasive whose future spread is thought to be affected by changes in climate. We investigated how mass at maturity varied with temperature (21°C, 25°C) across short and long photoperiods, using laboratory populations from the extreme ends of this species’ current US range (Florida, New Jersey). These values were used to parametrize a model to predict optimal mass based on development times; the results of a second laboratory experiment under the same treatments were compared to model predictions. Warmer conditions shortened development times in females from all locations leading to either higher or lower mass depending on the photoperiod. We then used published mass–fecundity relationships to determine the consequences of mass on fecundity under our conditions. Under the majority of scenarios warming decreased predicted fecundity under long photoperiods, but proved beneficial under short photoperiods because the costs of fast development were offset by increased survival in the face of late‐season freezing risk. However, fecundity was always low under short photoperiods, so the marginal benefit of warming appears negligible given its cost under long photoperiods when the majority of reproduction occurs. Thus, with northern range expansion, where colder weather currently limits this species, detrimental effects of warming on fecundity are likely, similar to those identified for mass. Unlike previous work that has shown benefits of a warming planet to insects like Aedes albopictus, our work predicts lower performance under warming conditions in summer across the current range, a prediction with implications for range expansion, disease dynamics and populations.     

Too hot to handle? Phenological and life‐history responses to simulated climate change of the southern green stink bug Nezara viridula (Heteroptera: Pentatomidae)

The effect of simulated climate change on Nezara viridula was studied close to the species' northern range limit in Japan. Insects from the same egg masses were reared for 15 months in 10 consecutive series under quasi‐natural (i.e. outdoor) conditions and in a transparent incubator, in which climate warming was simulated by adding 2.5 °C to the outdoor temperature. The warming strongly affected all life‐history and phenological parameters. In the spring, the simulated warming advanced the timing of postdiapause body colour changes and reproduction. In the early summer, it increased egg production and accelerated nymphal development. In the late summer (the hottest season), the effect of the simulated warming was strongly deleterious: nymphs developed slowly, suffered higher mortality and had difficulties during final moulting; the emerged females were smaller, some exhibited abnormal cuticle, produced fewer eggs and had a decreased life span. In the autumn, the warming accelerated nymphal development, resulted in larger female size, affected the timing of the diapause‐associated adult body colour change from green to russet and enhanced preparation for overwintering. Larger females had higher winter survival rate than smaller females. The warming strongly increased survival rate in both size classes and allowed smaller females to reach the same winter survival rate as larger females had under the quasi‐natural conditions. The winter survival also differed between the green and dark‐coloured females under the quasi‐natural, but not under the warming conditions. However, under the warming conditions, green females survived the winter even better than dark‐coloured females did under the quasi‐natural conditions. The warming also shortened the life span of females from the summer generations and prolonged it in those from the autumn generation. It is concluded that even a moderate temperature increase (+2.5 °C) in the future is likely to have a complex influence upon insects, strongly affecting many of their life‐history and phenological parameters.     

Russian wheat aphid (Hemiptera: Aphididae) reproduction and development on five noncultivated grass hosts

The Russian wheat aphid, Diuraphis noxia (Kurdjumov), is a small grains pest of worldwide economic importance. The Russian wheat aphid is polyphagous and may encounter differential selective pressures from noncultivated grass hosts. Aphid biotypic diversity can disrupt the progress of plant breeding programs, leading to a decreased ability to manage this pest. The goal of this research was to quantify Russian wheat aphid biotype 2 (RWA2) reproductive and development rates on five common noncultivated grass hosts to gain information about host quality, potential refuges, and sources of selection pressure. First, RWA2 reproduction was compared on crested wheatgrass (Agropyron cristatum, (L.) Gaertn.), intermediate wheatgrass (Elytrigia intermedia, (Host) Nevski), slender wheatgrass (Elymus trachycaulus, (Link) Gould ex Shinners), western wheatgrass (Pascopyrum smithi, (Rydb.) A. L?ve), and foxtail barley (Hordeum jubatum, (L.) Tesky) at 18–24°C. Second, RWA2 reproduction was compared on intermediate and crested wheatgrass at three temperature regimes 13–18°C, 18–24°C, and 24–29°C. At moderate temperatures (18–24°C), the intrinsic rate of increase values for all five hosts ranged from 0.141 to 0.199, indicating the possibility for strong population sources on all tested hosts. Aphids feeding on crested and intermediate wheatgrass at the 13–18°C temperature had lower fecundity, less nymph production days, longer generational times, and lower intrinsic rate of increase than aphids feeding at the 18–24°C temperature regime. Aphids feeding at 24–29°C did not survive long enough to reproduce. The positive intrinsic rates of increase in Russian wheat aphid on the wheatgrasses suggest that these grasses can support aphid populations at moderate to low temperatures.     

The cost of living for freshwater fish in a warmer, more polluted world

Little of the vast literature on the temperature physiology of freshwater fish is useful in predicting the effects of global warming. In the present review a series of laboratory experiments is reviewed in which rainbow trout (Oncorhynchus mykiss) were exposed to simulated global warming, a 2 °C increment superimposed upon the natural thermal regime, in the presence and absence of two common freshwater pollutants, ammonia and acidity (low pH). Simulated global warming had little effect on the growth and physiology of trout fed to satiation over much of the summer. However, in late summer, when ambient water temperature was at its highest, the addition of 2 °C caused a marked inhibition of appetite and growth, although this impact was not exacerbated by a reduction in food availability. In winter, + 2 °C stimulated metabolism, appetite and growth by approximately 30–60%. Exposure of satiation‐fed trout to low levels of pollutants produced unexpected results. Ammonia (NH₃ + NH₄⁺ = 70 μm) stimulated summer growth and energy conversion efficiency, whilst acidification (pH 5.2) increased appetite and growth but caused no disturbance of electrolyte balance. These pollutant effects were additive upon, but not synergistic with, the effects of + 2 °C. The ability of the fish to acclimate to the experimental conditions was tested with acute lethal temperature and/or toxicant challenges. Fish exposed to + 2 °C had a slightly (0.2–1.0 °C) but significantly higher lethal temperature than those exposed to ambient temperature when fed to satiation. However, there was no evidence of acclimation to either ammonia or low pH. It is concluded that the impact of global warming on freshwater fish will vary seasonally. The additional temperature may provide growth benefits in winter, but may threaten fish populations living towards the upper end of their thermal tolerance zone in (late) summer.     

Life on the edge: thermal optima for aerobic scope of equatorial reef fishes are close to current day temperatures

Equatorial populations of marine species are predicted to be most impacted by global warming because they could be adapted to a narrow range of temperatures in their local environment. We investigated the thermal range at which aerobic metabolic performance is optimum in equatorial populations of coral reef fish in northern Papua New Guinea. Four species of damselfishes and two species of cardinal fishes were held for 14 days at 29, 31, 33, and 34 °C, which incorporated their existing thermal range (29–31 °C) as well as projected increases in ocean surface temperatures of up to 3 °C by the end of this century. Resting and maximum oxygen consumption rates were measured for each species at each temperature and used to calculate the thermal reaction norm of aerobic scope. Our results indicate that one of the six species, Chromis atripectoralis, is already living above its thermal optimum of 29 °C. The other five species appeared to be living close to their thermal optima (ca. 31 °C). Aerobic scope was significantly reduced in all species, and approached zero for two species at 3 °C above current‐day temperatures. One species was unable to survive even short‐term exposure to 34 °C. Our results indicate that low‐latitude reef fish populations are living close to their thermal optima and may be more sensitive to ocean warming than higher‐latitude populations. Even relatively small temperature increases (2–3 °C) could result in population declines and potentially redistribution of equatorial species to higher latitudes if adaptation cannot keep pace.     

Climate‐induced shift in hydrological regime alters basal resource dynamics in a wilderness river ecosystem

1. We integrated a 20‐year ecological data set from a sparsely inhabited, snowmelt‐dominated catchment with hydrologic models to predict the effects of hydrologic shifts on stream biofilm. 2. We used a stepwise multiple regression to assess the relationship between hydrology and biofilm ash‐free dry mass (AFDM) and chlorophyll‐a (chl‐a) under recent climate conditions. Biofilm AFDM was significantly related to the timing of peak streamflow, and chl‐a was significantly related to the timing of median streamflow. We applied these results to output from the variable infiltration capacity hydrologic model, which predicted hydrology under a baseline scenario (+0 °C) and a range of warming scenarios expected with climate change (+1, +2 or +3 °C). 3. When compared to the baseline, the results indicated that earlier peakflows predicted under warming scenarios may lead to earlier initiation of biofilm growth. This may increase biofilm AFDM during the summer by up to 103% (±29) in the +3 °C scenario. Moreover, interannual variability of AFDM was predicted to increase up to 300%. Average chl‐a during the summer increased by up to 90% (±15) in the +3 °C scenario; however, its response was not significantly different from baseline in most years. 4. Because hydrologic change may alter the temporal dynamics of biofilm growth, it may affect the seasonal dynamics of biofilm quality (i.e. chl‐a‐to‐AFDM ratio). The results indicated that hydrologic shifts may increase biofilm quality during the spring, but may decrease it during the summer. Thus, we provide evidence that predicted hydrologic shifts in snowmelt‐dominated streams may alter the quantity and quality of an important basal resource. However, the magnitudes of these predictions are likely to be affected by other environmental changes that are occurring with climate change (e.g. increased wildfire activity and stream warming).     

Seedling survival of three endemic and threatened Mexican cacti under induced climate change

Human‐induced warming may increase the risk of local extinction for plant species with low tolerance of elevated temperatures. The Chihuahuan desert harbors the highest diversity of globose cacti in the world and most of them are at risk of extinction. Predictive models of climate change indicate an increase in summer temperature of 1–2°C by 2030 for this desert. Nevertheless, studies on the vulnerability of cacti species in early development phases to future climate change are scarce. We assessed the survival of three threatened cacti species from the Chihuahuan desert under induced warming. Open‐top chambers (OTCs) were used to simulate the effect of global warming on 2‐year seedlings of Echinocactus platyacanthus f. visnaga, Ferocactus histrix and Stenocactus coptonogonus. OTCs had higher temperature and lower humidity than control plots, and these elevated temperatures reduced seedling survival. Within the OTCs, no living individuals of any species were found after 105 days. Conversely, in the control plots, the three cacti species showed variable numbers of survivors after this period. Therefore the predicted global warming scenarios will greatly limit plant recruitment and the long‐term persistence of natural populations of Mexican endemic cacti species.     

Biodiversity bottleneck: seedling establishment under changing climatic conditions at the boreal–temperate ecotone

Climate change is increasing global temperatures, severe rainfall events, and the occurrence and severity of drought. Changes in global climate may have negative consequences for particular plant species and for biodiversity overall. In the short term, altered temperature and precipitation regimes may have the most severe effects on plant species near their range limits and in the earliest stages of plant development. To address these issues, we assessed seedling emergence, early survival, and growth of 18 boreal, temperate, and exotic woody species at the boreal–temperate forest ecotone in central Minnesota. We experimentally warmed forest plots to mimic projected warming by the end of the twenty-first century (+ 1.7 °C and + 3.4 °C). We also experimentally removed summer rainfall (~?42% reduction) to simulate drought conditions in this region. We found that emergence and survival of boreal and exotic species was lower in experimentally warmed plots. This was exacerbated by drought. Temperate species emergence and survival was largely unaffected by climate manipulations (on average). Conversely, temperate seedling growth was greater in warmer conditions, but only when paired with drought. We found that overall seedling species richness was reduced by warming, mostly due to lower boreal and exotic species emergence and survival (conifers were also strongly negatively affected across species-range groups). If temperate seedling emergence and survival does not compensate for loss of boreal species, these forests may experience loss of biodiversity (and associated ecosystem functions) in the future.     

Are winter-active species vulnerable to climate warming? A case study with the wintergreen terrestrial orchid,Tipularia discolor

In the eastern United States, winter temperature has been increasing nearly twice as fast as summer temperature, but studies of warming effects on plants have focused on species that are photosynthetically active in summer. The terrestrial orchid Tipularia discolor is leafless in summer and acquires C primarily in winter. The optimum temperature for photosynthesis in T. discolor is higher than the maximum temperature throughout most of its growing season, and therefore growth can be expected to increase with warming. Contrary to this hypothesis, experimental warming negatively affected reproductive fitness (number of flowering stalks, flowers, fruits) and growth (change in leaf area from 2010 to 2012) in T. discolor. Temperature in June–July was critical for flowering, and mean July temperature greater than 29 °C (i.e., 2.5 °C above ambient) eliminated reproduction. Warming of 1.2 °C delayed flowering by an average of 10 days and fruiting by an average of 5 days. Warming of 4.4 °C reduced relative growth rates by about 60 %, which may have been partially caused by the direct effects of temperature on photosynthesis and respiration. Warming indirectly increased vapor pressure deficit (VPD) by 0.2–0.5 kPa, and leaf-to-air VPD over 1.3 kPa restricted stomatal conductance of T. discolor to 10–40 % of maximum conductance. These results highlight the need to account for changes in VPD when estimating temperature responses of plant species under future warming scenarios. Increasing temperature in the future will likely be an important limiting factor to the distribution of T. discolor, especially along the southern edge of its range.     

Evidence for developmental thermal acclimation in the damselfish, Pomacentrus moluccensis

Tropical species are predicted to have limited capacity for acclimation to global warming. This study investigated the potential for developmental thermal acclimation by the tropical damselfish Pomacentrus moluccensis to ocean temperatures predicted to occur over the next 50–100 years. Newly settled juveniles were reared for 4 months in four temperature treatments, consisting of the current-day summer average (28.5 °C) and up to 3 °C above the average (29.5, 30.5 and 31.5 °C). Resting metabolic rate (RMR) of fish reared at 29.5 and 31.5 °C was significantly higher than the control group reared at 28.5 °C. In contrast, RMR of fish reared at 30.5 °C was not significantly different from the control group, indicating these fish had acclimated to their rearing temperature. Furthermore, fish that developed in 30.5 and 31.5 °C exhibited an enhanced ability to deal with acute temperature increases. These findings illustrate that developmental acclimation may help coral reef fish cope with warming ocean temperatures.     

Experimental warming alters the relative survival and emigration of two dung beetle species from an Australian dung pat community

To preserve insect‐mediated ecosystem services under ongoing climate change, it is necessary to first understand the impact that warming will have on the insects that provide or mediate these services. Furthermore, because responses of a species may be modified by interactions with competitors, it is informative to examine warming effects on organisms and service provision under competition. Dung beetles provide numerous services to agriculture by burying the manure of other animals. To understand the potential impacts of climate warming on ecosystem service provision, we exposed two dung beetle species (Sisyphus rubrus and Euoniticellus fulvus (Coleoptera: Scarabaeidae)), occurring together in the same experimental pats, to warming and measured reproduction (dung ball production and burial, brood production, and egg laying), pat departure behaviour and survival of both species. These two species are likely competitors in pastures in northern New South Wales. To simulate climate warming, we used custom‐built chambers to add offsets (+0, +2 or +4°C) to field recorded, diurnally fluctuating baseline temperatures. There was no direct effect of increased temperature on any measured trait in either species. We did find however that the relative survival of the two species depended on temperature; S. rubrus had a higher probability (resulting in greater odds) of surviving than E. fulvus in the +0 and +4°C offset chambers, but not in the +2°C offset chambers. Likewise, the relative likelihood of the different species leaving a dung pat was temperature dependent; in the +2°C offset chambers, E. fulvus were more likely to leave than S. rubrus, but not in the +0 and +4°C offsets chambers. Our results highlight that it may be important for future studies to consider warming effects on relative survival and emigration because such effects could potentially lead to changes in dung beetle species composition.     

Life stage‐dependent effects of experimental heat waves on an insect herbivore

1. Worldwide concern about the consequences of climate change has prompted efforts to understand and predict the responses of populations to changes in temperature. 2. A heat wave can adversely affect organisms, may affect different life stages differently, and could decrease populations. In this study, green peach aphid [Myzus persicae (Sulzer)] nymphs, reproductive adults, and late‐reproductive adults were exposed to a heat wave, defined as 5 °C above the control temperature regime for five consecutive days. 3. The negative effects of experimental warming on development, reproduction, and survival negatively affected population growth. Nymphs and reproductive adults were more severely impacted than late‐reproductive adults. 4. Experiments designed to mimic temperature regimes can assess the direct effects of climate change on individuals and populations. Our study highlights the importance of assessing the life stage‐specific responses to heat stress.     

Aphids in the face of global changes

Global warming is one of the principal challenges facing insects worldwide. It affects individual species and interactions between species directly through effects on their physiology and indirectly through effects on their habitat. Aphids are particularly sensitive to temperature changes due to certain specific biological features of this group. Effects on individuals have repercussions for aphid diversity and population dynamics. At a pan-European scale, the EXAMINE observation network has provided evidence for an increase in the number of aphid species present over the last 30 years and for earlier spring flights. We review these results and provide a review of the principal effects of global warming on aphid communities.     

The capacity to cope with climate warming declines from temperate to tropical latitudes in two widely distributed Eucalyptus species

As rapid climate warming creates a mismatch between forest trees and their home environment, the ability of trees to cope with warming depends on their capacity to physiologically adjust to higher temperatures. In widespread species, individual trees in cooler home climates are hypothesized to more successfully acclimate to warming than their counterparts in warmer climates that may approach thermal limits. We tested this prediction with a climate‐shift experiment in widely distributed Eucalyptus tereticornis and E. grandis using provenances originating along a ~2500 km latitudinal transect (15.5–38.0°S) in eastern Australia. We grew 21 provenances in conditions approximating summer temperatures at seed origin and warmed temperatures (+3.5 °C) using a series of climate‐controlled glasshouse bays. The effects of +3.5 °C warming strongly depended on home climate. Cool‐origin provenances responded to warming through an increase in photosynthetic capacity and total leaf area, leading to enhanced growth of 20–60%. Warm‐origin provenances, however, responded to warming through a reduction in photosynthetic capacity and total leaf area, leading to reduced growth of approximately 10%. These results suggest that there is predictable intraspecific variation in the capacity of trees to respond to warming; cool‐origin taxa are likely to benefit from warming, while warm‐origin taxa may be negatively affected.     

Reforestation and surface cooling in temperate zones: Mechanisms and implications

Land‐use/cover change (LUCC) is an important driver of environmental change, occurring at the same time as, and often interacting with, global climate change. Reforestation and deforestation have been critical aspects of LUCC over the past two centuries and are widely studied for their potential to perturb the global carbon cycle. More recently, there has been keen interest in understanding the extent to which reforestation affects terrestrial energy cycling and thus surface temperature directly by altering surface physical properties (e.g., albedo and emissivity) and land–atmosphere energy exchange. The impacts of reforestation on land surface temperature and their mechanisms are relatively well understood in tropical and boreal climates, but the effects of reforestation on warming and/or cooling in temperate zones are less certain. This study is designed to elucidate the biophysical mechanisms that link land cover and surface temperature in temperate ecosystems. To achieve this goal, we used data from six paired eddy‐covariance towers over co‐located forests and grasslands in the temperate eastern United States, where radiation components, latent and sensible heat fluxes, and meteorological conditions were measured. The results show that, at the annual time scale, the surface of the forests is 1–2°C cooler than grasslands, indicating a substantial cooling effect of reforestation. The enhanced latent and sensible heat fluxes of forests have an average cooling effect of ?2.5°C, which offsets the net warming effect (+1.5°C) of albedo warming (+2.3°C) and emissivity cooling effect (?0.8°C) associated with surface properties. Additional daytime cooling over forests is driven by local feedbacks to incoming radiation. We further show that the forest cooling effect is most pronounced when land surface temperature is higher, often exceeding ?5°C. Our results contribute important observational evidence that reforestation in the temperate zone offers opportunities for local climate mitigation and adaptation.     

Sensitivity of mangrove soil organic matter decay to warming and sea level change

Mangroves are among the world's most carbon‐dense ecosystems, but they are threatened by rapid climate change and rising sea levels. The accumulation and decomposition of soil organic matter (SOM) are closely tied to mangroves' carbon sink functions and resistance to rising sea levels. However, few studies have investigated the response of mangrove SOM dynamics to likely future environmental conditions. We quantified how mangrove SOM decay is affected by predicted global warming (+4°C), sea level changes (simulated by altering of the inundation duration to 0, 2, and 6 hr/day), and their interaction. Whilst changes in inundation duration between 2 and 6 hr/day did not affect SOM decay, the treatment without inundation led to a 60% increase. A warming of 4°C caused SOM decay to increase by 21%, but longer inundation moderated this temperature‐driven increase. Our results indicate that (a) sea level rise is unlikely to decrease the SOM decay rate, suggesting that previous mangrove elevation gain, which has allowed mangroves to persist in areas of sea level rise, might result from changes in root production and/or mineral sedimentation; (b) sea level fall events, predicted to double in frequency and area, will cause periods of intensified SOM decay; (c) changing tidal regimes in mangroves due to sea level rise might attenuate increases in SOM decay caused by global warming. Our results have important implications for forecasting mangrove carbon dynamics and the persistence of mangroves and other coastal wetlands under future scenarios of climate change.     

Prevailing sea surface temperatures inhibit summer reproduction of the kelp Laminaria digitata at Helgoland (North Sea)

The impact of abiotic factors on kelp sporophyte reproduction has rarely been investigated. Laminaria digitata (Hudson) J.V. Lamouroux is one of the few summer fertile Laminaria species worldwide and reproduction is subjected to relatively high water temperatures. We investigated the impact of prevailing summer temperatures (~18°C in August) on the induction of sporangia, meiospore release, and germination at the island of Helgoland (North Sea). At Helgoland, fertile sporophytes are found between April and December with a maximum in late summer. While released meiospore numbers were constant between June and October, germination rates decreased significantly in summer. Short‐term exposure of mature sori to 17°C–22°C induced a significantly higher meiospore release indicating enhancement of sporulation by elevated temperatures. Induction of sporangia on vegetative blade disks was not possible at 20°C, and fertility was only 20% at 18°C–19°C, but it was 100% in cool temperatures of 1°C–10°C. It was shown for the first time in a kelp species that “sporogenesis” is the life‐cycle process with the narrowest temperature window compared to growth or survival of the sporophyte or reproduction, growth, and survival of the gametophyte. We incorporated several parameters (induction time, fertile area, and relative fertility) into a “Reproductive efficiency index.” This indicates that sporogenesis of L. digitata is a cold‐adapted process with an optimum at (5)–10°C. The results show that the population at Helgoland is at its reproduction limit despite the existence of other geographically more southerly located populations.     

Forage plants of an Arctic‐nesting herbivore show larger warming response in breeding than wintering grounds,potentially disrupting migration phenology

During spring migration, herbivorous waterfowl breeding in the Arctic depend on peaks in the supply of nitrogen‐rich forage plants, following a “green wave” of grass growth along their flyway to fuel migration and reproduction. The effects of climate warming on forage plant growth are expected to be larger at the Arctic breeding grounds than in temperate wintering grounds, potentially disrupting this green wave and causing waterfowl to mistime their arrival on the breeding grounds. We studied the potential effect of climate warming on timing of food peaks along the migratory flyway of the Russian population of barnacle geese using a warming experiment with open‐top chambers. We measured the effect of 1.0–1.7°C experimental warming on forage plant biomass and nitrogen concentration at three sites along the migratory flyway (temperate wintering site, temperate spring stopover site, and Arctic breeding site) during 2 months for two consecutive years. We found that experimental warming increased biomass accumulation and sped up the decline in nitrogen concentration of forage plants at the Arctic breeding site but not at temperate wintering and stop‐over sites. Increasing spring temperatures in the Arctic will thus shorten the food peak of nitrogen‐rich forage at the breeding grounds. Our results further suggest an advance of the local food peak in the Arctic under 1–2°C climate warming, which will likely cause migrating geese to mistime their arrival at the breeding grounds, particularly considering the Arctic warms faster than the temperate regions. The combination of a shorter food peak and mistimed arrival is likely to decrease goose reproductive success under climate warming by reducing growth and survival of goslings after hatching.     

Symbiont infection affects aphid defensive behaviours

Aphids harbour both an obligate bacterial symbiont, Buchnera aphidicola, and a wide range of facultative ones. Facultative symbionts can modify morphological, developmental and physiological host traits that favour their spread within aphid populations. We experimentally investigated the idea that symbionts may also modify aphid behavioural traits to enhance their transmission. Aphids exhibit many behavioural defences against enemies. Despite their benefits, these behaviours have some associated costs leading to reduction in aphid reproduction. Some aphid individuals harbour a facultative symbiont Hamiltonella defensa that provides protection against parasitoids. By analysing aphid behaviours in the presence of parasitoids, we showed that aphids infected with H. defensa exhibited reduced aggressiveness and escape reactions compared with uninfected aphids. The aphid and the symbiont have both benefited from these behavioural changes: both partners reduced the fitness decrements associated with the behavioural defences. Such symbiont-induced changes of behavioural defences may have consequences for coevolutionary processes between host organisms and their enemies.