Abstract
Climate change is rapidly altering the way current species interact with their environment to satisfy life-history demands. In areas anticipated to experience extreme warming, rising temperatures are expected to diminish population growth, due either to environmental degradation, or the inability to tolerate novel temperature regimes. Determining how at risk ectotherms, and lizards in particular, are to changes in climate traditionally emphasizes the thermal ecology and thermal sensitivity of physiology of adult members of a population. In this study, we reveal ontogenetic differences in thermal physiological and ecological traits that have been used to anticipate how ectotherms will respond to climate change. We show that the thermal biological traits of juvenile Yarrow’s Spiny Lizards (Sceloporus jarrovii) differ from the published estimates of the same traits for adult lizards. Juvenile S. jarrovii differ in their optimal performance temperature, field field-active body temperature, and critical thermal temperatures compared to adult S. jarrovii. Within juvenile S. jarrovii, males and females exhibit differences in field-active body temperature and desiccation tolerance. Given the observed age- and sex-related variation in thermal physiology, we argue that not including physiological differences in thermal biology throughout ontogeny may lead to misinterpretation of patterns of ecological or evolutionary change due to climate warming. Further characterizing the potential for ontogenetic changes in thermal biology would be useful for a more precise and accurate estimation of the role of thermal physiology in mediating population persistence in warmer environments.
Highlights
Understanding how thermal environments influence physiological and ecological traits of ectothermic taxa has become a common practice in predicting organismal responses to novel thermal regimes [1,2,3]
evaporative water loss (EWL) rates were not influenced by snout-vent length (SVL) (F1, 62 = 1.11, P = 0.29), mass (F1, 62 = 2.08, P = 0.15), or body condition (F1, 62 = 0.001, P = 0.97)
We found no difference in Ts between the sexes (F1, 61 = 0.255, P = 0.62), but lizards with greater SVLs had greater Ts than smaller lizards (F1, 60 = 6.136, P = 0.016)
Summary
Understanding how thermal environments influence physiological and ecological traits of ectothermic taxa has become a common practice in predicting organismal responses to novel thermal regimes [1,2,3]. Ontogenetic Variation in S. jarrovii Thermal Biology of a species is used to infer their potential range of responses a species might exhibit This approach has enhanced our understanding of the relationship between thermal biology and species persistence in warmer environments, it often overlooks consideration of earlier life history stages, and potential ontogenetic variation in thermal physiological or ecological traits [12,13]. If such ontogenetic variation occurs, distinct life stages (e.g. adults and juveniles) should differ in their susceptibility to climate change. Models seeking to accurately predict species responses to climate change would require examination of multiple relevant life history stages in a species
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