Browsing by Author "Carter, Mauricio J."

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    Body size variation in polyplacophoran molluscs: Geographical clines and community structure along the south‐eastern Pacific
    (2021) Ibáñez, Christian M. ; Carter, Mauricio J. ; Aguilera, Moisés A. ; Pardo‐Gandarillas, M. Cecilia ; Rezende, Enrico L. ; Tomasovych, Adam
    Aim To evaluate the latitudinal pattern of body size within and among chiton species employing phylogenetically structured analyses and examine the role ofgeographical variation in temperature, productivity and oxygen availability as potential environmental drivers. Location Coastal habitats of the south-eastern Pacific along a latitudinal range of nearly 6,000 km, from the equator to Patagonia (c. 2 degrees to 56 degrees S). Time period Present (2011-2017). Major taxa studied Thirty-one species of polyplacophoran molluscs. Methods We measured the body length of 6,162 individuals collected in 62 sites, and reconstructed the phylogeny of this group based on two mitochondrial and one nuclear gene regions. We combined this information with data of sea surface temperature, chlorophyll-a concentration-as a proxy of primary productivity-and dissolved oxygen, and assessed which variables best explain the variation in size both within and among species employing phylogenetic generalized least squares (PGLS) and a model comparison approach. Main conclusions Our analyses show that body size increases consistently with latitude, both within and among species, following Bergmann's rule. Variation in sea surface temperature along the latitudinal gradient provided a substantially better fit than chlorophyll-a and dissolved oxygen. Our results support the temperature-size rule for this lineage and suggest that similar processes could underlie the emergence of intra- and interspecific gradients in body size of polyplacophorans. At the community level, chiton species richness was higher at intermediate latitudes and positively correlated with body size variation, suggesting that heterogeneity in size may reduce interspecific competition and contribute to species coexistence in this group. Overall, our study demonstrates that historical events, macroecological adaptive trends and local processes at the community level contribute to the distribution and size variation of polyplacophoran species throughout the south-eastern Pacific.
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    Cumulative Heat Stress in Fluctuating Temperatures and Implications for the Distribution of Freshwater Fish
    (John Wiley and Sons Inc, 2024) Rezende Landaeta, Enrico; Carter, Mauricio J.
    Predicting how rising temperatures will impact different species and communities is imperative and increasingly urgent with ongoing global warming. Here, we describe how thermal–death time curves obtained in the laboratory can be combined with an envelope model to predict the mortality of freshwater fish under field conditions and their distribution limits. We analyze the heat tolerance and distribution of 22 fish species distributed across North America and demonstrate that high temperatures imposed a distribution boundary for 11 of them, employing a null model. Importantly, predicted thermal boundaries closely match the warmest suitable locality of the envelope model. Simulated warming suggests that the distribution of fish species with lower heat tolerances will be disproportionately affected by rising temperatures, and the rate of local extinctions will be higher across fish communities in warmer localities. Ultimately, our analyses illustrate how physiological information can be combined with distribution models to forecast how warming temperatures are expected to impact different species and ecological communities.
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    Heat tolerance of marine ectotherms in a warming Antarctica
    (2023) Molina, Andres N.; Pulgar, Jose M.; Rezende, Enrico L.; Carter, Mauricio J.
    Global warming is affecting the Antarctic continent in complex ways. Because Antarctic organisms are specialized to living in the cold, they are vulnerable to increasing temperatures, although quantitative analyses of this issue are currently lacking. Here we compiled a total of 184 estimates of heat tolerance belonging to 39 marine species and quantified how survival is affected concomitantly by the intensity and duration of thermal stress. Species exhibit thermal limits displaced toward colder temperatures, with contrasting strategies between arthropods and fish that exhibit low tolerance to acute heat challenges, and brachiopods, echinoderms, and molluscs that tend to be more sensitive to chronic exposure. These differences might be associated with mobility. A dynamic mortality model suggests that Antarctic organisms already encounter temperatures that might be physiologically stressful and indicate that these ecological communities are indeed vulnerable to ongoing rising temperatures.
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    Individual variation in heat tolerance and metabolism in marine Antarctic organisms
    (2024) Varas, Oscar; Molina, Andres N.; Garcia-Huidobro, M. Roberto; Aldana, Marcela; Rezende, Enrico L.; Carter, Mauricio J.; Galban-Malagon, Cristobal; Pulgar, Jose M.
    Climate change is one of the main concerns to Antarctic biodiversity. Since temperature plays a crucial role in various biological traits, it is key to understand how warming may affect organisms specialized to live in the cold habitats. Although heat tolerance of several polar species is known, little emphasis has been given to individual variation and its relationship with other biological traits such as metabolic performance. In this study, we investigated the association between thermal sensitivity in metabolism (Q10) and heat tolerance (z) in six Antarctic marine organisms, including two fish species (Harpagifer antarcticus and Notothenia coriiceps), three crustaceans (Bovallia gigantea, Glyptonotus antarcticus, and Paraceradocus miersi), and one mollusk (Trophon nucelliformis). For this, we measured routine metabolic rates (RMR, mg O2/h) followed by heat tolerance measurements to reconstruct dose-response curves employing sublethal assays or thermal-collapse time (TCT) curves. Analyses reveal a negative relationship between the intercept and the slope of the temperature tolerance curves (CTmax and z values, respectively) against Q10, but only when T. nucelliformis was included in the generalized linear model. Therefore Q10 may be a good predictor of heat tolerance, but it is not true for chordate or arthropod species studied. Additionally, CTmax and z values exhibited a positive relationship consistent with previous studies. This study represents the first example of temperature tolerance curves quantified on an individual basis, and the analyses provide some evidence that thermal sensitivity in metabolism and heat tolerance are correlated. In future studies, it will be crucial to determine whether this relationship is robust and how it may impact the response of different lineages to accelerated warming.
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    Phylogeography of the subterranean rodent Spalacopus cyanus (Caviomorpha, Octodontidae)
    (ALLIANCE COMMUNICATIONS GROUP DIVISION ALLEN PRESS, 2008) Opazo, Juan C.; Bugueno, Manuel P.; Carter, Mauricio J.; Palma, R. Eduardo; Bozinovic, Francisco
    Spalacopus cyanus is a subterranean rodent inhabiting coastal and mountain habitats. Individuals from mountain populations are larger than individuals from the coast, and mountain populations have a more limited geographic range. To investigate the genetic structure and biogeography of this species, we analyzed mitochondrial DNA control region sequences. We found low levels of nucleotide diversity in comparison with other subterranean rodents. Coastal populations had higher nucleotide diversity and effective population size than mountain populations. Phylogenetic analysis using maximum parsimony and a haplotype network generated using statistical parsimony recognized 3 groups of haplotypes: northern coastal and mountain populations, central coastal populations, and southern coastal population. Consistent with the presence of unshared haplotypes, migration rates were practically 0, except from Valparaiso to Ventanas and from La Parva to Huentelauquen. We observed asymmetric migration rates from mountain to coastal populations, suggesting that this species originated in the Andean mountains. A likelihood ration test could not reject the null hypothesis of a stable population when all sequences were grouped into a single population and when coastal populations were analyzed separately. However, a negative exponential growth parameter was estimated for mountain populations,suggesting that these populations have undergone recent demographic changes.
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    Plasticity cannot fully compensate evolutionary differences in heat tolerance across fish species
    (2024) Molina, Andres N.; Carter, Mauricio J.; Rezende, Enrico L.
    Understanding how evolution and phenotypic plasticity contribute to variation in heat tolerance is crucial to predicting responses to warming. Here, we analyze 272 thermal death time curves of 53 fish species acclimated to different temperatures and quantify their relative contributions. Analyses show that evolution and plasticity account, respectively, for 80.5% and 12.4% of the variation in elevation across curves, whereas their slope remained invariant. Evolutionary and plastic adaptive responses differ in magnitude, with heat tolerance increasing to 0.54 degrees C between species and 0.32 degrees C within species for every 1 degrees C increase in environmental temperatures. After successfully predicting critical temperatures under ramping conditions to validate these estimates, we show that fish populations can only partly ameliorate the impact of warming waters via thermal acclimation, and this deficit in plasticity could increase as the warming accelerates.
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    Temperature variability and metabolic adaptation in terrestrial and aquatic ectotherms
    (2023) Carter, Mauricio J.; Cortes, Pablo A.; Rezende, Enrico L.
    Thermodynamics is a major factor determining rates of energy expenditure, rates of biochemical dynamics, and ultimately the biological and ecological processes linked with resilience to global warming in ectothermic organisms. Nonetheless, whether ectothermic organisms exhibit general adaptive metabolic responses to cope with worldwide variation in thermal conditions has remained as an open question. Here we combine a model comparison approach with a global dataset of standard metabolic rates (SMR), including 1,160 measurements across 788 species of aquatic invertebrates, insects, fishes, amphibians and reptiles, to investigate the association between metabolic rates and environmental temperatures in their respective habitats. Our analyses suggest that variation in SMR after removing allometric and thermodynamic effects is best explained by the temperature range encountered across seasons, which always provided a better fit than the average temperature for the hottest and coldest month and mean annual temperatures. This pattern was consistent across taxonomic groups and robust to sensitivity analyses. Nonetheless, aquatic and terrestrial lineages responded differently to seasonality, with SMR declining - 6.8% degrees C- 1 of thermal range across seasons in aquatic organisms and increasing 2.8% degrees C- 1 in terrestrial organisms. These responses may reflect alternative strategies to mitigate the impact of increments in warmer temperatures on energy expenditure, either by means of metabolic reduction in thermally homogeneous water bodies or effective behavioral thermoregulation to exploit temperature heterogeneity on land.
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    Upper thermal limits and risk of mortality of coastal Antarctic ectotherms
    (2023) Carter, Mauricio J.; Garcia-Huidobro, M. Roberto; Aldana, Marcela; Rezende, Enrico L.; Bozinovic, Francisco; Galban-Malagon, Cristobal; Pulgar, Jose M.
    Antarctic marine animals face one of the most extreme thermal environments, characterized by a stable and narrow range of low seawater temperatures. At the same time, the Antarctic marine ecosystems are threatened by accelerated global warming. Determining the upper thermal limits (CTmax) is crucial to project the persistence and distribution areas of the Antarctic marine species. Using thermal death time curves (TDT), we estimated CTmax at different temporal scales from 1 minute to daily and seasonal, the predict vulnerability to the current thermal variation and two potential heatwave scenarios. Our results revealed that CTmax at 1 min are far from the temperature present in the marine intertidal area where our study species, showing Echinoderm species higher CTmax than the Chordata and Arthropods species. Simulations indicated that seasonal thermal variation from the intertidal zone contributed to basal mortality, which increased after considering moderate scenarios of heatwaves (+2 degrees C) in the Shetland Archipelago intertidal zone. Our finding highlighted the relevance of including exposure time explicitly on the CTmax estimates, which deliver closer and more realistic parameters according to the species that may be experiencing in the field.