Predicting the biodiversity impacts of global warming implies that we know where and with what magnitude these impacts will be encountered. Amphibians are currently the most threatened vertebrates, mainly due to habitat loss and to emerging infectious diseases. Global warming may further exacerbate their decline in the near future, although the impact might vary geographically. We predicted that subtropical amphibians should be relatively susceptible to warming-induced extinctions because their upper critical thermal limits (CT max ) might be only slightly higher than maximum pond temperatures (T max ). We tested this prediction by measuring CT max and T max for 47 larval amphibian species from two thermally distinct subtropical communities (the warm community of the Gran Chaco and the cool community of Atlantic Forest, northern Argentina), as well as from one European temperate community. Upper thermal tolerances of tadpoles were positively correlated (controlling for phylogeny) with maximum pond temperatures, although the slope was steeper in subtropical than in temperate species. CT max values were lowest in temperate species and highest in the subtropical warm community, which paradoxically, had very low warming tolerance (CT max -T max ) and therefore may be prone to future local extinction from acute thermal stress if rising pond T max soon exceeds their CT max . Canopy-protected subtropical cool species have larger warming tolerance and thus should be less impacted by peak temperatures. Temperate species are relatively secure to warming impacts, except for late breeders with low thermal tolerance, which may be exposed to physiological thermal stress in the coming years.

Although temperature variation is known to cause large-scale adaptive divergence, its potential role as a selective factor over microgeographic scales is less well-understood. Here, we investigated how variation in breeding pond temperature affects divergence in multiple physiological (thermal performance curve and critical thermal maximum [CTmax]) and life-history (thermal developmental reaction norms) traits in a network of Rana arvalis populations. The results supported adaptive responses to face two main constraints limiting the evolution of thermal adaptation. First, we found support for the faster-slower model, indicating an adaptive response to compensate for the thermodynamic constraint of low temperatures in colder environments. Second, we found evidence for the generalist-specialist trade-off with populations from colder and less thermally variable environments exhibiting a specialist phenotype performing at higher rates but over a narrower range of temperatures. By contrast, the local optimal temperature for locomotor performance and CTmax did not match either mean or maximum pond temperatures. These results highlight the complexity of the adaptive multiple-trait thermal responses in natural populations, and the role of local thermal variation as a selective force driving diversity in life-history and physiological traits in the presence of gene flow.

To forecast biological responses to changing environments, we need to understand how a species's physiology varies through space and time and assess how changes in physiological function due to environmental changes may interact with phenotypic changes caused by other types of environmental variation. Amphibian larvae are well known for expressing environmentally induced phenotypes, but relatively little is known about how these responses might interact with changing temperatures and their thermal physiology. To address this question, we studied the thermal physiology of grey treefrog tadpoles (Hyla versicolor) by determining whether exposures to predator cues and an herbicide (Roundup) can alter their critical maximum temperature (CTmax) and their swimming speed across a range of temperatures, which provides estimates of optimal temperature (Topt) for swimming speed and the shape of the thermal performance curve (TPC). We discovered that predator cues induced a 0.4°C higher CTmax value, whereas the herbicide had no effect. Tadpoles exposed to predator cues or the herbicide swam faster than control tadpoles and the increase in burst speed was higher near Topt. In regard to the shape of the TPC, exposure to predator cues increased Topt by 1.5°C, while exposure to the herbicide marginally lowered Topt by 0.4°C. Combining predator cues and the herbicide produced an intermediate Topt that was 0.5°C higher than the control. To our knowledge this is the first study to demonstrate a predator altering the thermal physiology of amphibian larvae (prey) by increasing CTmax, increasing the optimum temperature, and producing changes in the thermal performance curves. Furthermore, these plastic responses of CTmax and TPC to different inducing environments should be considered when forecasting biological responses to global warming.

Some marine animals have a dynamic mutualistic association involving heterotrophic coral animals (hosts) and autotrophic dinoflagellate endosymbionts in the genus Symbiodinium, known as zooxanthellae, which are directly involved in their physiology. Currently, there is limited knowledge of the Symbiodinium diversity associated with zoanthids from the Brazilian coast. Hence, this study assessed the diversity of zooxanthellae associated with Palythoa caribaeorum, Zoanthus sociatus and Protopalythoa variabilis commonly found on the northeast coast. Zoanthids samples were collected from sandstone reefs, and the total DNA from the samples was extracted. Diversity was assessed by denaturing gradient gel electrophoresis (DGGE) and ITS region cloning library. Data from ITS region sequences showed that zoanthids hosted two phylogenetic subclades or subgenus (C1 and A3) closely related to Symbiodinium from previous studies. Subclade C1 was found in Pa. caribaeorum, Pr. variabilis and Z. sociatus, while subclade A3 was found exclusively in Z. sociatus. This suggests that Pa. caribaeorum and Pr. variabilis are extremely selective, whereas Z. sociatus shows greater flexibility in the selection of its symbionts, and these differences may be involved with living in different reef environments. Knowledge of zooxanthellae diversity associated with zoanthids can explain their large distribution in Brazilian coast and contribute to a better understanding of zoanthid's sensitivity to thermal stress.

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