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How species respond to climate change will depend on the collective response of populations. Intraspecific variation in traits, evolved through genetic adaptation and phenotypic plasticity, can cause thermal performance curves to vary over species' distributions. Intraspecific variation within marine species has received relatively little attention due to the belief that marine systems lack dispersal barriers strong enough to promote locally adapted traits. Here we show that intraspecific variation is present between low- and high-latitude populations of a coral reef damselfish (Acanthochromis polyacanthus). Co-gradient variation was observed when examining aerobic physiology across a thermal gradient that reflected mean summer temperatures of high- and low-latitude regions, as well as projected future ocean temperatures (i.e. 27, 28.5, 30, 31.5°C). Whilst thermally sensitive, no significant differences were observed between high- and low-latitude regions when measuring immunocompetence, haematocrit and anaerobic enzyme activity. The presence of co-gradient variation suggests that dispersal limitations in marine systems can promote local adaptive responses; however, intraspecific variation may not be ubiquitous amongst traits. Identifying locally adapted traits amongst populations remains necessary to accurately project species responses to climate change and identify differences in adaptive potential.
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Tropical ectotherms are highly sensitive to environmental warming, especially coral reef fishes, which are negatively impacted by an increase of a few degrees in ocean temperature. However, much of our understanding on the thermal sensitivity of reef fish is focused on a few traits (e.g., metabolism, reproduction) and we currently lack knowledge on warming effects on cognition, which may endanger decision-making and survival. Here, we investigated the effects of warming on learning and memory in a damselfish species, Acanthochromis polyacanthus. Fish were held at 28-28.5 °C (control group), 30-30.5 °C (moderate warming group) or 31.5-32 °C (high warming group) for 2 weeks, and then trained to associate a blue tag (cue) to the presence of a conspecific (reward). Following 20 training trials (5 days), fish were tested for associative learning (on the following day) and memory storage (after a 5-days interval). The control group A. polyacanthus showed learning of the task and memory retention after five days, but increasing water temperature impaired learning and memory. A thorough understanding of the effects of heat stress, cognition, and fitness is urgently required because cognition may be a key factor determining animals' performance in the predicted scenario of climate changes. Knowing how different species respond to warming can lead to better predictions of future community dynamics, and because it is species specific, it could pinpoint vulnerable/resilience species.
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Arrecifes de Coral , Perciformes , Animales , Peces , Cambio Climático , Océanos y MaresRESUMEN
Rising ocean temperatures are threatening marine species and populations worldwide, and ectothermic taxa are particularly vulnerable. Echinoderms are an ecologically important phylum of marine ectotherms and shifts in their population dynamics can have profound impacts on the marine environment. The effects of warming on echinoderms are highly variable across controlled laboratory-based studies. Accordingly, synthesis of these studies will facilitate the better understanding of broad patterns in responses of echinoderms to ocean warming. Herein, a meta-analysis incorporating the results of 85 studies (710 individual responses) is presented, exploring the effects of warming on various performance predictors. The mean responses of echinoderms to all magnitudes of warming were compared across multiple biological responses, ontogenetic life stages, taxonomic classes, and regions, facilitated by multivariate linear mixed effects models. Further models were conducted, which only incorporated responses to warming greater than the projected end-of-century mean annual temperatures at the collection sites. This meta-analysis provides evidence that ocean warming will generally accelerate metabolic rate (+32%) and reduce survival (-35%) in echinoderms, and echinoderms from subtropical (-9%) and tropical (-8%) regions will be the most vulnerable. The relatively high vulnerability of echinoderm larvae to warming (-20%) indicates that this life stage may be a significant developmental bottleneck in the near-future, likely reducing successful recruitment into populations. Furthermore, asteroids appear to be the class of echinoderms that are most negatively affected by elevated temperature (-30%). When considering only responses to magnitudes of warming representative of end-of-century climate change projections, the negative impacts on asteroids, tropical species and juveniles were exacerbated (-51%, -34% and -40% respectively). The results of these analyses enable better predictions of how keystone and invasive echinoderm species may perform in a warmer ocean, and the possible consequences for populations, communities and ecosystems.
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Nearly a billion people depend on tropical seascapes. The need to ensure sustainable use of these vital areas is recognised, as one of 17 policy commitments made by world leaders, in Sustainable Development Goal (SDG) 14 ('Life below Water') of the United Nations. SDG 14 seeks to secure marine sustainability by 2030. In a time of increasing social-ecological unpredictability and risk, scientists and policymakers working towards SDG 14 in the Asia-Pacific region need to know: (1) How are seascapes changing? (2) What can global society do about these changes? and (3) How can science and society together achieve sustainable seascape futures? Through a horizon scan, we identified nine emerging research priorities that clarify potential research contributions to marine sustainability in locations with high coral reef abundance. They include research on seascape geological and biological evolution and adaptation; elucidating drivers and mechanisms of change; understanding how seascape functions and services are produced, and how people depend on them; costs, benefits, and trade-offs to people in changing seascapes; improving seascape technologies and practices; learning to govern and manage seascapes for all; sustainable use, justice, and human well-being; bridging communities and epistemologies for innovative, equitable, and scale-crossing solutions; and informing resilient seascape futures through modelling and synthesis. Researchers can contribute to the sustainability of tropical seascapes by co-developing transdisciplinary understandings of people and ecosystems, emphasising the importance of equity and justice, and improving knowledge of key cross-scale and cross-level processes, feedbacks, and thresholds.
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The parental environment can alter offspring phenotypes via the transfer of non-genetic information. Parental effects may be viewed as an extension of (within-generation) phenotypic plasticity. Smaller size, poorer physical condition, and skewed sex ratios are common responses of organisms to global warming, yet whether parental effects alleviate, exacerbate, or have no impact on these responses has not been widely tested. Further, the relative non-genetic influence of mothers and fathers and ontogenetic timing of parental exposure to warming on offspring phenotypes is poorly understood. Here, we tested how maternal, paternal, and biparental exposure of a coral reef fish (Acanthochromis polyacanthus) to elevated temperature (+1.5°C) at different ontogenetic stages (development vs reproduction) influences offspring length, weight, condition, and sex. Fish were reared across two generations in present-day and projected ocean warming in a full factorial design. As expected, offspring of parents exposed to present-day control temperature that were reared in warmer water were shorter than their siblings reared in control temperature; however, within-generation plasticity allowed maintenance of weight, resulting in a higher body condition. Parental exposure to warming, irrespective of ontogenetic timing and sex, resulted in decreased weight and condition in all offspring rearing temperatures. By contrast, offspring sex ratios were not strongly influenced by their rearing temperature or that of their parents. Together, our results reveal that phenotypic plasticity may help coral reef fishes maintain performance in a warm ocean within a generation, but could exacerbate the negative effects of warming between generations, regardless of when mothers and fathers are exposed to warming. Alternatively, the multigenerational impact on offspring weight and condition may be a necessary cost to adapt metabolism to increasing temperatures. This research highlights the importance of examining phenotypic plasticity within and between generations across a range of traits to accurately predict how organisms will respond to climate change.
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Global warming is expected to drive some ectothermic species beyond their thermal tolerance in upcoming decades. Phenotypic plasticity, via developmental or transgenerational acclimation, is a critical mechanism for compensation in the face of environmental change. Yet, it remains to be determined if the activation of beneficial phenotypes requires direct exposure throughout development, or if compensation can be obtained just through the experience of previous generations. In this study, we exposed three generations of a tropical damselfish to combinations of current-day (Control) and projected future (+1.5°C) water temperatures. Acclimation was evaluated with phenotypic (oxygen consumption, hepatosomatic index, physical condition) and molecular (liver gene expression) measurements of third-generation juveniles. Exposure of grandparents/parents to warm conditions improved the aerobic capacity of fish regardless of thermal conditions experienced afterwards, representing a true transgenerational effect. This coincided with patterns of gene expression related to inflammation and immunity seen in the third generation. Parental effects due to reproductive temperature significantly affected the physical condition and routine metabolic rate (oxygen consumption) of offspring, but had little impact on gene expression of the F3. Developmental temperature of juveniles, and whether they matched conditions during parental reproduction, had the largest influence on the liver transcriptional program. Using a combination of both phenotypic and molecular approaches, this study highlights how the conditions experienced by both previous and current generations can influence plasticity to global warming in upcoming decades.
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Global warming can disrupt reproduction or lead to fewer and poorer quality offspring, owing to the thermally sensitive nature of reproductive physiology. However, phenotypic plasticity may enable some animals to adjust the thermal sensitivity of reproduction to maintain performance in warmer conditions. Whether elevated temperature affects reproduction may depend on the timing of exposure to warming and the sex of the parent exposed. We exposed male and female coral reef damselfish (Acanthochromis polyacanthus) during development, reproduction or both life stages to an elevated temperature (+1.5°C) consistent with projected ocean warming and measured reproductive output and newly hatched offspring performance relative to pairs reared in a present-day control temperature. We found female development in elevated temperature increased the probability of breeding, but reproduction ceased if warming continued to the reproductive stage, irrespective of the male's developmental experience. Females that developed in warmer conditions, but reproduced in control conditions, also produced larger eggs and hatchlings with greater yolk reserves. By contrast, male development or pairs reproducing in higher temperature produced fewer and poorer quality offspring. Such changes may be due to alterations in sex hormones or an endocrine stress response. In nature, this could mean female fish developing during a marine heatwave may have enhanced reproduction and produce higher quality offspring compared with females developing in a year of usual thermal conditions. However, male development during a heatwave would likely result in reduced reproductive output. Furthermore, the lack of reproduction from an average increase in temperature could lead to population decline. Our results demonstrate how the timing of exposure differentially influences females and males and how this translates to effects on reproduction and population sustainability in a warming world.
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AbstractClimate change and population irruptions of crown-of-thorns sea stars (Acanthaster sp.) are two of the most pervasive threats to coral reefs. Yet there has been little consideration regarding the synergies between ocean warming and the coral-feeding sub-adult and adult stages of this asteroid. Here we explored the thermosensitivity of the aforementioned life stages by assessing physiological responses to acute warming. Thermal sensitivity was assessed based on the maximal activity of enzymes involved in aerobic (citrate synthase) and anaerobic (lactate dehydrogenase) metabolic pathways, as well as the standard metabolic rate of sub-adult and adult sea stars. In both life stages, citrate synthase activity declined with increasing temperature from 15 °C to 40 °C, with negligible activity occurring >35 °C. On the other hand, lactate dehydrogenase activity increased with temperature from 20 °C to 45 °C, indicating a greater reliance on anaerobic metabolism in a warmer environment. The standard metabolic rate of sub-adult sea stars increased with temperature throughout the testing range (24 °C to 36 °C). Adult sea stars exhibited evidence of thermal stress, with metabolic depression occurring from 33 °C. Here, we demonstrate that crown-of-thorns sea stars are sensitive to warming but that adults, and especially sub-adults, may have some resilience to short-term marine heatwaves in the near future.
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Antozoos , Estrellas de Mar , Animales , Arrecifes de Coral , Estrellas de Mar/fisiología , TemperaturaRESUMEN
BACKGROUND AND OVERVIEW: Endodontics is a rewarding and challenging profession. The tasks of negotiating, cleaning, and shaping canals can frustrate even the most talented clinicians, particularly if the canals are blocked by calcifications. Circumventing these obstructions can be a slow, tedious process, and at times it is not possible. Various techniques have been developed to assist with this problem but have met with limited success. Given that the success of endodontic treatment is dependent on the elimination or reduction of bacterial influences on periapical tissues, this is a critical issue. CASE DESCRIPTION: A new application of an existing technology is available. This technique uses 3-dimensional (3D) radiography (cone-beam computed tomography) and 3D intraoral imaging. Through the integration of the data sets, pathways are planned to locate blocked canals. Templates can be designed and fabricated on 3D printers that fit intimately on the dentition. Special drills are selected that fit through the sleeves embedded in the template. These pathways align the drill and guide the depth of the access. Once the canals are accessed, conventional root canal treatment is possible. CONCLUSIONS AND PRACTICAL IMPLICATIONS: This case report reviews a new technique for treating a necrotic calcified root canal. The canal was identified in the apical one-third of the root. A pathway was planned to negotiate the canal using digital technology. The blockage was bypassed, and the root canal was successfully treated using a "template-guided access technique" with minimal tooth loss.
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Cavidad Pulpar , Endodoncia , Tomografía Computarizada de Haz Cónico , Cavidad Pulpar/diagnóstico por imagen , Humanos , Imagenología Tridimensional , Tratamiento del Conducto RadicularRESUMEN
Rising water temperature and increased uptake of CO2 by the ocean are predicted to have widespread impacts on marine species. However, the effects are likely to vary, depending on a species' sensitivity and the geographical location of the population. Here, we investigated the potential effects of elevated temperature and pCO2 on larval growth and survival in a New Zealand population of the Australasian snapper, Chrysophyrs auratus. Eggs and larvae were reared in a fully cross-factored experiment (18 °C and 22 °C/pCO2 440 and 1040 µatm) to 16 days post hatch (dph). Morphologies at 1 dph and 16 dph were significantly affected by temperature, but not CO2. At 1dph, larvae at 22 °C were longer (7%) and had larger muscle depth at vent (14%), but had reduced yolk (65%) and oil globule size (16%). Reduced yolk reserves in recently hatched larvae suggests higher metabolic demands in warmer water. At 16 dph, larvae at elevated temperature were longer (12%) and muscle depth at vent was larger (64%). Conversely, survival was primarily affected by CO2 rather than temperature. Survivorship at 1 dph and 16 dph was 24% and 54% higher, respectively, under elevated CO2 compared with ambient conditions. Elevated temperature increased survival (24%) at 1 dph, but not at 16 dph. These results suggest that projected climate change scenarios may have an overall positive effect on early life history growth and survival in this population of C. auratus. This could benefit recruitment success, but needs to be weighed against negative effects of elevated CO2 on metabolic rates and swimming performance observed in other studies on the same population.
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Dióxido de Carbono , Cambio Climático , Animales , Larva , Agua de Mar , Natación , TemperaturaRESUMEN
Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms. Changes to individual growth rates could then flow on to influence emergent properties of social groups, particularly in species that form size-based hierarchies. To test the potential interactive effects of (1) food availability, (2) elevated CO2 during juvenile development, and (3) parental experience of elevated CO2 on the growth, condition and size-based hierarchy of juvenile fish, we reared orange clownfish (Amphiprion percula) for 50 days post-hatching in a fully orthogonal design. Development in elevated CO2 reduced standard length and weight of juveniles, by 9% and 11% respectively, compared to ambient. Development under low food availability reduced length and weight of juveniles by 7% and 15% respectively, compared to high food. Parental exposure to elevated CO2 restored the length of juveniles to that of controls, but it did not restore weight, resulting in juveniles from elevated CO2 parents exhibiting 33% lower body condition when reared in elevated CO2. The body size ratios (relative size of a fish from the rank above) within juvenile groups were not affected by any treatment, suggesting relative robustness of group-level structure despite alterations in individual size and condition. This study demonstrates that both food availability and elevated CO2 can influence the physical attributes of juvenile reef fish, but these changes may not disrupt the emergent group structure of this social species, at least amongst juveniles.
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Tamaño Corporal , Dióxido de Carbono/farmacología , Arrecifes de Coral , Alimentos , Jerarquia Social , Perciformes/anatomía & histología , Perciformes/crecimiento & desarrollo , Animales , Tamaño Corporal/efectos de los fármacos , Femenino , MasculinoRESUMEN
Ocean warming associated with global climate change is already inducing geographic range shifts of marine species. Juvenile coral reef fishes transported into temperate latitudes (termed 'vagrant' fishes) can experience winter water temperatures below their normal thermal minimum. Such environmental extremes may increase energetic costs for such fishes, resulting in reduced performance, which may be the governing factor that limits the potential for poleward range expansion of such fishes. This study compared the juvenile physiological performance and behaviour of two congeneric tropical damselfishes which settle during austral summer months within temperate eastern Australia: Abudefduf vaigiensis have an extended southern range, and lower threshold survival temperature than the congeneric A. whitleyi. Physiological and behavioural performance parameters that may be affected by cooler temperature regimes at higher latitudes were measured in aquaria. Lower water temperature resulted in reduced growth rates, feeding rates, burst escape speed and metabolic rates of both species, with significantly reduced performance (up to six-fold reductions) for fishes reared at 18 °C relative to 22 °C and 26 °C. However, A. whitleyi exhibited lower growth rates than A. vaigiensis across all temperatures, and lower aerobic capacity at the lowest temperature (18 °C). This difference between species in growth and metabolic capacity suggests that the extended southern distribution and greater overwintering success of A. vaigiensis, in comparison to A. whitleyi is related to thermal performance parameters which are critical in maintaining individual health and survival. Our results support previous findings in the region that water temperature below 22 °C represents a critical physiological threshold for tropical Abudefduf species expatriating into temperate south-eastern Australia.
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Distribución Animal , Arrecifes de Coral , Peces/fisiología , Calentamiento Global , Animales , TemperaturaRESUMEN
Marine heatwaves, which are increasing in frequency, duration and intensity owing to climate change, are an imminent threat to marine ecosystems. On coral reefs, heatwave conditions often coincide with periods of peak recruitment of juvenile fishes and exposure to elevated temperature may affect their development. However, whether differences in the duration of high temperature exposure have effects on individual performance is unknown. We exposed juvenile spiny damselfish, Acanthochromis polyacanthus, to increasing lengths of time (3, 7, 30 and 108â days post-hatching) of elevated temperature (+2°C). After 108â days, we measured escape performance at present-day control and elevated temperatures, standard length, mass and critical thermal maximum. Using a Bayesian approach, we show that 30â days or more exposure to +2°C leads to improved escape performance, irrespective of performance temperature, possibly owing to developmental effects of high temperature on muscle development and/or anaerobic metabolism. Continued exposure to elevated temperature for 108â days caused a reduction in body size compared with the control, but not in fish exposed to high temperature for 30â days or less. By contrast, exposure to elevated temperatures for any length of time had no effect on critical thermal maximum, which, combined with previous work, suggests a short-term physiological constraint of â¼37°C in this species. Our study shows that extended exposure to increased temperature can affect the development of juvenile fishes, with potential immediate and future consequences for individual performance.
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Arrecifes de Coral , Peces/crecimiento & desarrollo , Calor , Rasgos de la Historia de Vida , Animales , Teorema de Bayes , Calentamiento Global , Calor/efectos adversos , Factores de TiempoRESUMEN
How populations and species respond to modified environmental conditions is critical to their persistence both now and into the future, particularly given the increasing pace of environmental change. The process of adaptation to novel environmental conditions can occur via two mechanisms: (1) the expression of phenotypic plasticity (the ability of one genotype to express varying phenotypes when exposed to different environmental conditions), and (2) evolution via selection for particular phenotypes, resulting in the modification of genetic variation in the population. Plasticity, because it acts at the level of the individual, is often hailed as a rapid-response mechanism that will enable organisms to adapt and survive in our rapidly changing world. But plasticity can also retard adaptation by shifting the distribution of phenotypes in the population, shielding it from natural selection. In addition to which, not all plastic responses are adaptive-now well-documented in cases of ecological traps. In this theme issue, we aim to present a considered view of plasticity and the role it could play in facilitating or hindering adaption to environmental change. This introduction provides a re-examination of our current understanding of the role of phenotypic plasticity in adaptation and sets the theme issue's contributions in their broader context. Four key themes emerge: the need to measure plasticity across both space and time; the importance of the past in predicting the future; the importance of the link between plasticity and sexual selection; and the need to understand more about the nature of selection on plasticity itself. We conclude by advocating the need for cross-disciplinary collaborations to settle the question of whether plasticity will promote or retard species' rates of adaptation to ever-more stressful environmental conditions. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.
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Adaptación Fisiológica , Evolución Biológica , Cambio Climático , Ambiente , Selección Genética , GenotipoRESUMEN
Climate change is leading to shifts in species geographical distributions, but populations are also probably adapting to environmental change at different rates across their range. Owing to a lack of natural and empirical data on the influence of phenotypic adaptation on range shifts of marine species, we provide a general conceptual model for understanding population responses to climate change that incorporates plasticity and adaptation to environmental change in marine ecosystems. We use this conceptual model to help inform where within the geographical range each mechanism will probably operate most strongly and explore the supporting evidence in species. We then expand the discussion from a single-species perspective to community-level responses and use the conceptual model to visualize and guide research into the important yet poorly understood processes of plasticity and adaptation. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.
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Adaptación Fisiológica , Organismos Acuáticos/fisiología , Ecosistema , Geografía , Modelos Biológicos , Océanos y MaresRESUMEN
Global warming will have far-reaching consequences for marine species over coming decades, yet the magnitude of these effects may depend on the rate of warming across generations. Recent experiments show coral reef fishes can compensate the metabolic challenges of elevated temperature when warm conditions are maintained across generations. However, the effects of a gradual temperature increase across generations remain unknown. In the present study, we analysed metabolic and molecular traits in the damselfish Acanthochromis polyacanthus that were exposed to +1.5°C in the first generation and +3.0°C in the second (Step +3.0°C). This treatment of stepwise warming was compared to fish reared at current-day temperatures (Control), second-generation fish of control parents reared at +3.0°C (Developmental +3.0°C) and fish exposed to elevated temperatures for two generations (Transgenerational +1.5°C and Transgenerational +3.0°C). Hepatosomatic index, oxygen consumption and liver gene expression were compared in second-generation fish of the multiple treatments. Hepatosomatic index increased in fish that developed at +3.0°C, regardless of the parental temperature. Routine oxygen consumption of Step +3.0°C fish was significantly higher than Control; however, their aerobic scope recovered to the same level as Control fish. Step +3.0°C fish exhibited significant upregulation of genes related to mitochondrial activity and energy production, which could be associated with their increased metabolic rates. These results indicate that restoration of aerobic scope is possible when fish experience gradual thermal increase across multiple generations, but the metabolic and molecular responses are different from fish reared at the same elevated thermal conditions in successive generations.
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Aclimatación/genética , Calentamiento Global , Perciformes/genética , Temperatura , Animales , Arrecifes de Coral , Expresión Génica , Perciformes/fisiología , FenotipoRESUMEN
Climate change is expected to pose a significant risk to species that exhibit strong behavioural preferences for specific habitat types, with generalist species assumed to be less vulnerable. In this study, we conducted habitat choice experiments to determine how water temperature influences habitat preference for three common species of coral reef damselfish (Pomacentridae) that differ in their levels of habitat specialisation. The lemon damselfish Pomacentrus moluccensis, a habitat specialist, consistently selected complex coral habitat across all temperature treatments (selected based on local average seasonal temperatures naturally experienced in situ: ambient winter 22°C; ambient summer 28°C; and elevated 31°C). Unexpectedly, the neon damselfish Pomacentrus coelestis and scissortail sergeant Abudefduf sexfasciatus, both of which have more generalist habitat associations, developed strong habitat preferences (for complex coral and boulder habitat, respectively) at the elevated temperature treatment (31°C) compared to no single preferred habitat at 22°C or 28°C. The observed shifts in habitat preference with temperature suggest that we may be currently underestimating the vulnerability of some habitat generalists to climate change and highlight that the ongoing loss of complex live coral through coral bleaching could further exacerbate resource overlap and species competition in ways not currently considered in climate change models.
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Aclimatación , Cambio Climático , Arrecifes de Coral , Ecosistema , Perciformes/fisiología , Temperatura , Animales , Conducta Animal , Océanos y Mares , Perciformes/clasificación , Especificidad de la EspecieRESUMEN
Range shifts of tropical marine species to temperate latitudes are predicted to increase as a consequence of climate change. To date, the research focus on climate-mediated range shifts has been predominately dealt with the physiological capacity of tropical species to cope with the thermal challenges imposed by temperate latitudes. Behavioural traits of individuals in the novel temperate environment have not previously been investigated, however, they are also likely to play a key role in determining the establishment success of individual species at the range-expansion forefront. The aim of this study was to investigate the effect of shoaling strategy on the performance of juvenile tropical reef fishes that recruit annually to temperate waters off the south east coast of Australia. Specifically, we compared body-size distributions and the seasonal decline in abundance through time of juvenile tropical fishes that shoaled with native temperate species ('mixed' shoals) to those that shoaled only with conspecifics (as would be the case in their tropical range). We found that shoaling with temperate native species benefitted juvenile tropical reef fishes, with individuals in 'mixed' shoals attaining larger body-sizes over the season than those in 'tropical-only' shoals. This benefit in terms of population body-size distributions was accompanied by greater social cohesion of 'mixed' shoals across the season. Our results highlight the impact that sociality and behavioural plasticity are likely to play in determining the impact on native fish communities of climate-induced range expansion of coral reef fishes.