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Critical thermal limits (CTmax and CTmin) decrease with elevation, with greater change in CTmin, and the risk to suffer heat and cold stress increasing at the gradient ends. A central prediction is that populations will adapt to the prevailing climatic conditions. Yet, reliable support for such expectation is scant because of the complexity of integrating phenotypic, molecular divergence and organism exposure. We examined intraspecific variation of CTmax and CTmin, neutral variation for 11 microsatellite loci, and micro‐ and macro‐temperatures in larvae from 11 populations of the Galician common frog (Rana parvipalmata) across an elevational gradient, to assess (1) the existence of local adaptation through a PST‐FST comparison, (2) the acclimation scope in both thermal limits, and (3) the vulnerability to suffer acute heat and cold thermal stress, measured at both macro‐ and microclimatic scales. Our study revealed significant microgeographic variation in CTmax and CTmin, and unexpected elevation gradients in pond temperatures. However, variation in CTmax and CTmin could not be attributed to selection because critical thermal limits were not correlated to elevation or temperatures. Differences in breeding phenology among populations resulted in exposure to higher and more variable temperatures at mid and high elevations. Accordingly, mid‐ and high‐elevation populations had higher CTmax and CTmin plasticities than lowland populations, but not more extreme CTmax and CTmin. Thus, our results support the prediction that plasticity and phenological shifts may hinder local adaptation, promoting thermal niche conservatism. This may simply be a consequence of a coupled variation of reproductive timing with elevation (the "elevation‐time axis" for temperature variation). Mid and high mountain populations of R. parvipalmata are more vulnerable to heat and cool impacts than lowland populations during the aquatic phase. All of this contradicts some of the existing predictions on adaptive thermal clines and vulnerability to climate change in elevational gradients. [ABSTRACT FROM AUTHOR]

The climate variability hypothesis posits that increased environmental thermal variation should select for thermal generalists, while stable environments should favor thermal specialists. This hypothesis has been tested on large spatial scales, such as latitude and elevation, but less so on smaller scales reflective of the experienced microclimate. Here, we estimated thermal tolerance limits of 75 species of amphibian tadpoles from an aseasonal tropical mountain range of the Ecuadorian Andes, distributed along a 3500 m elevational range, to test the climatic variability hypothesis at a large (elevation) and a small (microhabitat) scale. We show how species from less variable thermal habitats, such as lowlands and those restricted to streams, exhibit narrower thermal tolerance breadths than highland and pond‐dwelling species respectively. Interestingly, while broader thermal tolerance breadths at large scales are driven by higher cold tolerance variation (heat‐invariant hypothesis), at local scales they are driven by higher heat tolerance variation. This contrasting pattern may result from divergent selection on both thermal limits to face environmental thermal extremes at different scales. Specifically, within the same elevational window, exposure to extreme maximum temperatures could be avoided through habitat shifts from temporary ponds to permanent ponds or streams, while minimum peak temperatures remained invariable between habitats but steadily decreased with elevation. Therefore an understanding of the effects of habitat conversion is crucial for future research on resilience to climate change. [ABSTRACT FROM AUTHOR]

Climate change may have dramatic consequences for communities through both direct effects of peak temperatures upon individual species and through interspecific mismatches in thermal sensitivities of interacting organisms which mediate changes in interspecific interactions (i.e. predation). Despite this, there is a paucity of information on the patterns of spatial physiological sensitivity of interacting species (at both landscape and local scales) which could ultimately influence geographical variation in the effects of climate change on community processes. In order to assess where these impacts may occur, we first need to evaluate the spatial heterogeneity in the degree of mismatch in thermal tolerances between interacting organisms.We quantify the magnitude of interspecific mismatch in maximum (CTmax) and minimum (CTmin) thermal tolerances among a predator–prey system of dragonfly and anuran larvae in tropical montane (242–3,631 m) and habitat (ponds and streams) gradients. To compare thermal mismatches between predator and prey, we coined the parameters maximum and minimum predatory tolerance margins (PTMmax and PTMmin), or difference in CTmax and CTmin of interacting organisms sampled across elevational and habitat gradients.Our analyses revealed that: (a) predators exhibit higher heat tolerances than prey (~4°C), a trend which remained stable across habitats and elevations. In contrast, we found no differences in minimum thermal tolerances between these groups. (b) Maximum and minimum thermal tolerances of both predators and prey decreased with elevation, but only maximum thermal tolerance varied across habitats, with pond species exhibiting higher heat tolerance than stream species. (c) Pond‐dwelling organisms from low elevations (0–1,500 m a.s.l.) may be more susceptible to direct effects of warming than their highland counterparts because their maximum thermal tolerances are only slightly higher than their exposed maximum environmental temperatures.The greater relative thermal tolerance of dragonfly naiad predators may further increase the vulnerability of lowland tadpoles to warming due to potentially enhanced indirect effects of higher predation rates by more heat‐tolerant dragonfly predators. However, further experimental work is required to establish the individual and population‐level consequences of this thermal tolerance mismatch upon biotic interactions such as predator–prey. ​ [ABSTRACT FROM AUTHOR]

Complex life-histories may promote the evolution of different strategies to allow optimal matching to the environmental conditions that organisms can encounter in contrasting environments. For ectothermic animals, we need to disentangle the role of stage-specific thermal tolerances and developmental acclimation to predict the effects of climate change on spatial distributions. However, the interplay between these mechanisms has been poorly explored. Here we study whether developmental larval acclimation to rearing temperatures affects the thermal tolerance of subsequent terrestrial stages (metamorphs and juveniles) in common frogs (Rana temporaria). Our results show that larval acclimation to warm temperatures enhances larval heat tolerance, but not thermal tolerance in later metamorphic and juvenile stages, which does not support the developmental acclimation hypothesis. Further, metamorphic and juvenile individuals exhibit a decline in thermal tolerance, which would confer higher sensitivity to extreme temperatures. Because thermal tolerance is not enhanced by larval developmental acclimation, these 'risky' stages may be forced to compensate through behavioural thermoregulation and short-term acclimation to face eventual heat peaks in the coming decades. [ABSTRACT FROM AUTHOR]