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.

In organisms with complex life cycles, environmentally induced plasticity across sequential stages can have important consequences on morphology and life history traits such as developmental and growth rates. However, previous research in amphibians and other ectothermic vertebrates suggests that some morphological traits are generally insensitive to environmental inductions. We conducted a literature survey to examine the allometric responses in relative hind leg length and head shape of post-metamorphic anuran amphibians to induced environmental (temperature, resource level, predation and desiccation risk) variation operating during the larval phase in 44 studies using 19 species. To estimate and compare plastic responses across studies, we employed both an index of plasticity and effect sizes from a meta-analysis. We found contrasting trait responses to different environmental cues. Higher temperatures increased development more than growth rate and induced smaller heads but not overall shifts in hind leg length. In contrast, an increment in resource availability increased growth more than development, with a parallel increase in hind leg length but no change in head shape. Increases in predation risk decreased both development and growth rates and slightly reduced relative hind leg length, but there was no change in head shape. Pond desiccation induced quick development and low growth rates, with no changes in morphology. Across environments, both hind leg and head shape plasticity were positively correlated with growth rate plasticity. However, plasticity of developmental rate was only correlated with head shape plasticity. Overall, these results suggest that environmental trends predicted by global warming projections, such as increasing pond temperature and accelerating pond desiccation, will significantly influence hind leg and head morphology in metamorphic frogs, which may affect performance and, ultimately, fitness.

In the toad Bufo calamita, among-population variation of size follows roughly a converse Bergmann cline, but populations exist that do not fit this pattern. We propose that latitudinal body size variation is a byproduct of adaptive covariation among the life-history traits juvenile growth rate, longevity and lifetime fecundity. We choose five populations (two in Andalusia, two in Catalonia and one in Rhineland-Palatinate) representing a variation of adult size from 39 mm to 95 mm snout-vent length, a latitudinal gradient from 37 to 501 and an altitudinal gradient from sea level to 420 m. Skeletochronology was used to estimate the age-related life-history traits of 313 toads and their lifetime pattern of growth. At southern latitudes, toads matured and reproduced earlier than those at northern latitudes, but had a reduced potential reproductive lifespan due to lower longevity. Ageadjusted adult size depended mainly on the size achieved between metamorphosis and first hibernation or aestivation, which in turn was influenced by local factors. We propose that first-year size corresponds to the duration of the aboveground activity period, temperature during the activity period and the type of shelter sites and hibernacula available in the habitat. After attaining sexual maturity, the growth rates did not differ among populations. Interactions of multiple environmental factors during the first year of life determine age at maturity, adult size and size variation among populations. Local body size and potential reproductive lifespan covary to optimize lifetime fecundity throughout the geographical range. The presence of a small-sized population in southern Spain does not fit the pattern predicted by a converse Bergmann cline, but is compatible with the hypothesis that body size variation among B. calamita populations may be the evolutionary byproduct of optimized lifetime fecundity.

Natale, G.S., Alcalde, L., Herrera, R., Cajade, R., Schaefer, E.F., Marangoni, F. and Trudeau, V.L. 2011. Underwater acoustic communication in the macrophagic carnivorous larvae of Ceratophrys ornata (Anura: Ceratophryidae). -Acta Zoologica (Stockholm) 92: 46-53.We provide the first evidence for sound production by anuran larvae. In this study, we describe the sounds, their context-specific emission and the structures related to sound production of the carnivorous larvae of Ceratophrys ornata (Amphibia, Anura, Ceratophryidae). Tadpoles emit a brief, clear and very audible metallic-like sound that consists of a short train of notes that occur at all stages of larval development. Tadpoles make sound only when a conspecific tadpole is preying upon it or when touched by an object. Ceratophrys ornata larvae possess the basic required anatomical structures for sound production via expulsion of atmospheric air from the lungs through the open soft-tissue glottis. The glottis is opened and closed via the larval laryngeal muscles (constrictor laryngis and dilatator laryngis). The arytenoid cartilages appear at stage 40 and the cricoid cartilage does at stage 43. Adult laryngeal muscles differentiate from the larval ones at stage 46 together with the vocal sac formation from the adult interhyoideus muscle. We demonstrate (n = 2160 conspecific predator-prey interactions) that larval sounds occur always under predatory attack, probably serving to diminish the chances of cannibalism. These data raise the possibility that other macrophagic carnivorous anuran larvae may produce sound.