Methods and pitfalls of measuring thermal preference and tolerance in lizards

Camacho, Agustín; Rusch, Travis W.

doi:10.1016/j.jtherbio.2017.03.010

Cited by 80 publications

(73 citation statements)

References 145 publications

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“…In contrast, critical‐thermal maxima (e.g., temperatures at which lizards cannot locomote) may be less relevant, since these are often much higher than VTM, and lizards would likely seek shelter and avoid these temperatures long before they were reached (Camacho et al, ). FBT represent body temperatures at which lizards are active, reflecting their preferred temperatures and those locally available (review in Camacho & Rusch, ).…”

Section: Methodsmentioning

confidence: 99%

Climate change, extinction, and Sky Island biogeography in a montane lizard

et al. 2019

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Around the world, many species are confined to “Sky Islands,” with different populations in isolated patches of montane habitat. How does this pattern arise? One scenario is that montane species were widespread in lowlands when climates were cooler, and were isolated by local extinction caused by warming conditions. This scenario implies that many montane species may be highly susceptible to anthropogenic warming. Here, we test this scenario in a montane lizard (Sceloporus jarrovii) from the Madrean Sky Islands of southeastern Arizona. We combined data from field surveys, climate, population genomics, and physiology. Overall, our results support the hypothesis that this species' current distribution is explained by local extinction caused by past climate change. However, our results for this species differ from simple expectations in several ways: (a) their absence at lower elevations is related to warm winter temperatures, not hot summer temperatures; (b) they appear to exclude a low‐elevation congener from higher elevations, not the converse; (c) they are apparently absent from many climatically suitable but low mountain ranges, seemingly “pushed off the top” by climates even warmer than those today; (d) despite the potential for dispersal among ranges during recent glacial periods (~18,000 years ago), populations in different ranges diverged ~4.5–0.5 million years ago and remained largely distinct; and (e) body temperatures are inversely related to climatic temperatures among sites. These results may have implications for many other Sky Island systems. More broadly, we suggest that Sky Island species may be relevant for predicting responses to future warming.

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Section: Methodsmentioning

confidence: 99%

Climate change, extinction, and Sky Island biogeography in a montane lizard

et al. 2019

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“…All of the lizards tested behaved normally after being cooled in this manner within 5–10 min of ending the CT max trial. While this is still the most commonly applied method to determine CT max , the repeated righting response method may exhaust lizards, and results should consequently be interpreted with caution (Camacho and Rusch ).…”

Section: Methodsmentioning

confidence: 99%

Thermoregulatory behavior and high thermal preference buffer impact of climate change in a Namib Desert lizard

et al. 2017

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Abstract. Knowledge of the thermal ecology of a species can improve model predictions for temperatureinduced population collapse, which in light of climate change is increasingly important for species with limited distributions. Here, we use a multi-faceted approach to quantify and integrate the thermal ecology, properties of the thermal habitat, and past and present distribution of the diurnal, xeric-adapted, and active-foraging Namibian lizard Pedioplanis husabensis (Sauria: Lacertidae) to model its local extinction risk under future climate change scenarios. We asked whether climatic conditions in various regions of its range are already so extreme that local extirpations of P. husabensis have already occurred, or whether this micro-endemic species is adapted to these extreme conditions and uses behavior to mitigate the environmental challenges. To address this, we collected thermoregulation and climate data at a micro-scale level and combined it with micro-and macroclimate data across the species' range to model extinction risk. We found that P. husabensis inhabits a thermally harsh environment, but also has high thermal preference. In cooler parts of its range, individuals are capable of leaving thermally favorable conditions-based on the species' thermal preference-unused during the day, probably to maintain low metabolic rates. Furthermore, during the summer, we observed that individuals regulate at body temperatures below the species' high thermal preference to avoid body temperatures approaching the critical thermal maximum. We find that populations of this species are currently persisting even at the hottest localities within the species' geographic distribution. We found no evidence of range shifts since the 1960s despite a documented increase in air temperatures. Nevertheless, P. husabensis only has a small safety margin between the upper limit of its thermal preference and the critical thermal maximum and might undergo range reductions in the near future under even the most moderate climate change scenarios.

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“…For all species, CT min and CT max were experimentally estimated as the lower and upper temperatures, respectively, at which a lizard failed to right itself when flipped on its back (Spellerberg 1972). Physiological variables are often subject to considerable noise (e.g., Camacho and Rusch 2017). To minimize noise, we excluded any measures of thermal limits gathered through different experimental end points (e.g., the onset of muscle spasms or lethal limits; Lutterschmidt and Hutchison 1997).…”

Section: Study Species and Data Collectionmentioning

confidence: 99%

Physiological evolution during adaptive radiation: A test of the island effect inAnolislizards

et al. 2019

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Phenotypic evolution is often exceptionally rapid on islands, resulting in numerous, ecologically diverse species. Although adaptive radiation proceeds along various phenotypic axes, the island effect of faster evolution has been mostly tested with regard to morphology. Here, we leveraged the physiological diversity and species richness of Anolis lizards to examine the evolutionary dynamics of three key traits: heat tolerance, body temperature, and cold tolerance. Contrary to expectation, we discovered slower heat tolerance evolution on islands. Additionally, island species evolve toward higher optimal body temperatures than mainland species. Higher optima and slower evolution in upper physiological limits are consistent with the Bogert effect, or evolutionary inertia due to thermoregulation. Correspondingly, body temperature is higher and more stable on islands than on the American mainland, despite similarity in thermal environments. Greater thermoregulation on islands may occur due to ecological release from competitors and predators compared to mainland environments. By reducing the costs of thermoregulation, ecological opportunity on islands may actually stymie, rather than hasten, physiological evolution. Our results emphasize that physiological diversity is an important axis of ecological differentiation in the adaptive radiation of anoles, and that behavior can impart distinct macroevolutionary footprints on physiological diversity on islands and continents.

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Methods and pitfalls of measuring thermal preference and tolerance in lizards

Cited by 80 publications

References 145 publications

Climate change, extinction, and Sky Island biogeography in a montane lizard

Climate change, extinction, and Sky Island biogeography in a montane lizard

Thermoregulatory behavior and high thermal preference buffer impact of climate change in a Namib Desert lizard

Physiological evolution during adaptive radiation: A test of the island effect inAnolislizards

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