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Aim: Life in mountains is associated with multiple features that increase the risk of demographic collapses in populations – small geographic ranges, short breeding seasons, specialization to harsh climates – leading to the hypothesis that extinction risk is exacerbated in species inhabiting higher elevations. Here, we implement the first test of this hypothesis across the amphibian tree of life – the tetrapods with the largest proportion of montane species, and nature's most threatened animals. Location: Global. Time Period: Present. Major Taxa Studied: Class Amphibia. Methods: We collated a dataset spanning 8042 species from across all three amphibian orders (Anura, Caudata and Gymnophiona). We preformed phylogenetic logistic regressions to test the predictions that extinction risk increases with elevation, and whether this effect is caused by factors previously hypothesised to drive high‐elevation declines, including restrictions on species' geographic ranges, variation in their life histories and the presence of infectious disease. Results: Globally, extinction risk increases towards higher elevations. At order‐level, this relationship holds for frogs and salamanders. Even when controlling for geographic range size, life histories and infectious disease, extinction risk increases with elevation for amphibians combined and frogs globally, and in the Americas. In contrast, whereas extinction risk is greater among high‐elevation Eurasian amphibians, this relationship is explained by larger body sizes and lower fecundity. Main Conclusions: Our analyses indicate that after considering factors previously thought to explain the increase in extinction risk towards higher elevations (e.g., geographic range size, disease), elevation remains a significant predictor of amphibian extinction risk. Given that the only available tests of this hypothesis in other tetrapods (birds and reptiles) conflict with our findings, we suggest that physiological or life‐history features of amphibians may explain this observed phenomenon. [ABSTRACT FROM AUTHOR]

Aim: The emergence of large‐scale patterns of animal body size is the central expectation of a wide range of (macro)ecological and evolutionary hypotheses. The drivers shaping these patterns include climate (e.g. Bergmann's rule), resource availability (e.g. 'resource rule'), biogeographic settings and niche partitioning (e.g. adaptive radiation). However, these hypotheses often make opposing predictions about the trajectories of body size evolution. Therefore, whether underlying drivers of body size evolution can be identified remains an open question. Here, we employ the most comprehensive global dataset of body size in amphibians, to address multiple hypotheses that predict patterns of body size evolution based on climatic factors, ecology and biogeographic settings to identify underlying drivers and their generality across lineages. Location: Global. Time Period: Present. Major Taxa Studied: Amphibians. Methods: Using a global dataset spanning 7270 (>87% of) species of Anura, Caudata and Gymnophiona, we employed phylogenetic Bayesian modelling to test the roles of climate, resource availability, insularity, elevation, habitat use and diel activity on body size. Results: Only climate and elevation drive body size patterns, and these processes are order‐specific. Seasonality in precipitation and in temperature predict body size clines in anurans, whereas caecilian body size increases with aridity. However, neither of these drivers explained variation in salamander body size. In both anurans and caecilians, size increases with elevational range and with midpoint elevation in caecilians only. No effects of mean temperature, resource abundance, insularity, time of activity or habitat use were found. Main Conclusions: Precipitation and temperature seasonality are the dominant climatic drivers of body size variation in amphibians overall. Bergmann's rule is consistently rejected, and so are other alternative hypotheses. We suggest that the rationale sustaining existing macroecological rules of body size is unrealistic in amphibians and discuss our findings in the context of the emerging hypothesis that climate change can drive body size shifts. [ABSTRACT FROM AUTHOR]

Aim: Rising ocean temperatures are widely recognized as the dominant driver behind the rapid degradation of coral reefs via the process of coral bleaching (the expulsion of photosynthetic endosymbionts, which reveals the coral skeleton). However, bleaching of hard corals is often assumed to be further aggravated by the effect of local‐scale stressors from anthropogenic activity, accelerating coral reef decline where these stressors are stronger. Despite the importance of this hypothesis, the interaction between climate change and local stressors for driving coral bleaching has only been investigated in a handful of studies, with no large scale (regional or global) test conducted thus far. We investigate the impact of human population density (HPD) – a proxy for local stressors – in both protected and non‐protected marine regions, and their interaction under heat stress as drivers of coral bleaching. Location: Global. Time period: 2002–2018. Major taxa studied: Scleractinia corals. Methods: Using 9,170 coral reef surveys worldwide, we performed Bayesian modelling to assess the probability of coral bleaching in response to local‐scale stressors in interaction with global warming. Results: Local HPD does not exacerbate coral bleaching, either independently or under thermal stress from climate change. Rather, the relationship between HPD and temperature stress appears weakly antagonistic for coral bleaching, contradicting the expectation that HPD increases sensitivity of corals to bleaching under thermal stress. Main conclusions: Local HPD does not interact with global warming for degrading coral reefs. However, regional variation in bleaching patterns exists. Consequently, bleaching will continue to occur on most coral reefs globally regardless of local HPD. Thus, it is likely that even isolated, well‐protected, coral reefs will continue to decline because of climate warming‐induced bleaching. Therefore, tackling the source of global warming remains the most effective way to mitigate coral reef decline via coral bleaching. [ABSTRACT FROM AUTHOR]