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Abstract The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog,Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (Tb), preferred body temperatures (Tpref), critical thermal maxima (CTmax), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater meanTbandTprefthan those from forests. In contrast,CTmaxandTSMdid not differ significantly between habitats. However,CTmaxdid increase moderately with increasingTb, suggesting that changes inCTmaxmay be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. AlthoughO. pumilioexhibited moderate divergence inTpref,CTmaxappears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain theirTbbelow air temperatures that reach or exceedCTmax. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming. Abstract in Spanish is available with online material.
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Asymmetry of thermal sensitivity and the thermal risk of climate change
Abstract AimUnderstanding and predicting the biological consequences of climate change requires considering the thermal sensitivity of organisms relative to environmental temperatures. One common approach involves ‘thermal safety margins’ (TSMs), which are generally estimated as the temperature differential between the highest temperature an organism can tolerate (critical thermal maximum, CTmax) and the mean or maximum environmental temperature it experiences. Yet, organisms face thermal stress and performance loss at body temperatures below their CTmax,and the steepness of that loss increases with the asymmetry of the thermal performance curve (TPC). LocationGlobal. Time period2015–2019. Major taxa studiedAnts, fish, insects, lizards and phytoplankton. MethodsWe examine variability in TPC asymmetry and the implications for thermal stress for 384 populations from 289 species across taxa and for metrics including ant and lizard locomotion, fish growth, and insect and phytoplankton fitness. ResultsWe find that the thermal optimum (Topt, beyond which performance declines) is more labile than CTmax, inducing interspecific variation in asymmetry. Importantly, the degree of TPC asymmetry increases with Topt. Thus, even though populations with higher Topts in a hot environment might experience above‐optimal body temperatures less often than do populations with lower Topts, they nonetheless experience steeper declines in performance at high body temperatures. Estimates of the annual cumulative decline in performance for temperatures above Toptsuggest that TPC asymmetry alters the onset, rate and severity of performance decrement at high body temperatures. Main conclusionsSpecies with the same TSMs can experience different thermal risk due to differences in TPC asymmetry. Metrics that incorporate additional aspects of TPC shape better capture the thermal risk of climate change than do TSMs.
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- Award ID(s):
- 1951356
- PAR ID:
- 10373488
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Global Ecology and Biogeography
- Volume:
- 31
- Issue:
- 11
- ISSN:
- 1466-822X
- Page Range / eLocation ID:
- p. 2231-2244
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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