Como a sazonalidade influencia a fisiologia térmica de lagartos com diferentes estratégias termorregulatórias: uma meta-análise
Data
2021-09-29
Autores
Oliveira, Danilo Giacometti dos Santos Uehara 
Orientadores
Barros, Fábio Cury de
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Ectotermos que mantêm o balanço térmico de forma relativamente independente às condições climáticas devem ser favorecidos a colonizar uma grande quantidade de habitats. Para minimizar influências externas sobre a fisiologia e controlar a temperatura corpórea, lagartos utilizam uma ampla gama de comportamentos termorregulatórios. Lagartos heliotérmicos usam a radiação solar para ganhar calor e são frequentemente vistas como termorreguladoras precisos. Contrariamente, não-heliotérmicos são geralmente limitados pelas condições climáticas de seus habitats e apresentam baixa precisão termorregulatória por conta disto. Embora muito foco tenha sido dado aos efeitos das temperaturas médias sobre as espécies, sabemos relativamente menos sobre como a sazonalidade da temperatura afeta respostas térmicas em ampla escala. Considerando a crise climática que estamos enfrentando, é extremamente importante entender como lagartos lidam com variações temporais e espaciais no clima. As temperaturas corpóreas de atividade (Tb) e as temperaturas preferenciais (Tpref) são traços-chave da fisiologia térmica que são frequentemente estudados no contexto de mudanças sazonais nas temperaturas do habitat. Neste trabalho, usamos uma abordagem meta-analítica para avaliar como a sazonalidade da temperatura influencia a variação sazonal na Tb e Tpref de lagartos com diferentes estratégias termorregulatórias (heliotérmicos vs. não-heliotérmicos). Nós mostramos que a magnitude da variação sazonal da Tb foi maior do que da Tpref, e isso pode ser explicado a partir das diferenças teóricas e metodológicas entre esses traços. Em habitats pouco sazonais, heliotérmicos mostraram menor variação na Tb do que não-heliotérmicos, em concordância com a noção de que heliotérmicos têm maior precisão termorregulatória. No entanto, em habitats muito sazonais, a variação na Tb de heliotérmicos aumentou, sugerindo que o comportamento termorregulatório pode não compensar os efeitos do clima sobre as espécies em locais em que as temperaturas ambientais variam substancialmente entre estações. A variação sazonal na Tpref aumentou com a sazonalidade da temperatura ambiental independente da estratégia termorregulatória. Isso indica que lagartos em ambientes muito sazonais têm maior potencial para plasticidade em respostas térmicas, sendo capazes de se manterem ativos apesar de grandes variações nas temperaturas corpóreas. Em suma, nossos resultados apoiam a ideia de que a fisiologia térmica tende a ser mais variável em ambientes mais sazonais e mostra que a importância relativa do comportamento termorregulatória depende do contexto em que as espécies estão inseridas. Nós reforçamos a importância de usar informações fisiológicas, comportamentais e ambientais em modelos que têm como objetivo entender os fatores que promovem ou limitam a evolução de traços térmicos.
Ectotherms that maintain thermal balance relatively independently of climatic conditions should be favoured to colonise a wide range of habitats. To buffer external influences of physiology and control body temperature, lizards use a variety of thermoregulatory behaviours. Heliothermic species rely on solar radiation to raise body temperatures and have been shown to thermoregulate precisely. In contrast, non-heliotherms are often constrained by climatic conditions in their habitats, thus having low thermoregulatory precision. While much focus has been given to the effects of mean habitat temperatures over lizards, relatively less is known about how temperature seasonality affects thermal responses on a large scale. Considering the climate crisis we are facing, it is of utmost importance to understand how lizards deal with spatial and temporal climatic variation. Activity body temperatures (Tb) and preferred body temperatures (Tpref) are key thermal physiology traits often studied in the context of seasonal changes in habitat temperatures. In this study, we used a meta-analytical approach to evaluate how temperature seasonality influenced the seasonal variation in Tb and Tpref of lizards with different thermoregulatory strategies (heliotherms vs. non-heliotherms). We showed that the magnitude of seasonal variation in Tb was greater than in Tpref, which is explained by theoretical and methodological dissimilarities between traits. In slightly seasonal habitats, heliotherms showed less Tb variation than non-heliotherms, in accordance to the notion that heliotherms have greater thermoregulatory precision. In highly seasonal habitats, however, variation in the Tb of heliotherms increased, suggesting that behaviour may not account for climatic effects over species when habitat temperatures vary substantially. The seasonal variation in Tpref increased with temperature seasonality regardless of whether species were heliotherms or non-heliotherms. This indicates that lizards in highly seasonal habitats have the greatest potential for plasticity in thermal responses, being able to sustain activity despite high fluctuations in body temperatures so long as thermoregulation is not costly. In sum, our results support the notion that thermal physiology tends to vary more in highly seasonal habitats, and show that the importance of thermoregulatory behaviours is context-dependent. We reinforce the importance of using physiological, behavioural, and environmental information in models that aim to understand the factors promote or hinder the evolution of thermal traits.
Ectotherms that maintain thermal balance relatively independently of climatic conditions should be favoured to colonise a wide range of habitats. To buffer external influences of physiology and control body temperature, lizards use a variety of thermoregulatory behaviours. Heliothermic species rely on solar radiation to raise body temperatures and have been shown to thermoregulate precisely. In contrast, non-heliotherms are often constrained by climatic conditions in their habitats, thus having low thermoregulatory precision. While much focus has been given to the effects of mean habitat temperatures over lizards, relatively less is known about how temperature seasonality affects thermal responses on a large scale. Considering the climate crisis we are facing, it is of utmost importance to understand how lizards deal with spatial and temporal climatic variation. Activity body temperatures (Tb) and preferred body temperatures (Tpref) are key thermal physiology traits often studied in the context of seasonal changes in habitat temperatures. In this study, we used a meta-analytical approach to evaluate how temperature seasonality influenced the seasonal variation in Tb and Tpref of lizards with different thermoregulatory strategies (heliotherms vs. non-heliotherms). We showed that the magnitude of seasonal variation in Tb was greater than in Tpref, which is explained by theoretical and methodological dissimilarities between traits. In slightly seasonal habitats, heliotherms showed less Tb variation than non-heliotherms, in accordance to the notion that heliotherms have greater thermoregulatory precision. In highly seasonal habitats, however, variation in the Tb of heliotherms increased, suggesting that behaviour may not account for climatic effects over species when habitat temperatures vary substantially. The seasonal variation in Tpref increased with temperature seasonality regardless of whether species were heliotherms or non-heliotherms. This indicates that lizards in highly seasonal habitats have the greatest potential for plasticity in thermal responses, being able to sustain activity despite high fluctuations in body temperatures so long as thermoregulation is not costly. In sum, our results support the notion that thermal physiology tends to vary more in highly seasonal habitats, and show that the importance of thermoregulatory behaviours is context-dependent. We reinforce the importance of using physiological, behavioural, and environmental information in models that aim to understand the factors promote or hinder the evolution of thermal traits.