ABSTRACT
Functional traits are those characteristics of organisms that influence the ability of a species to develop in a habitat and persist in the face of environmental changes. The traits are often affected by a multiplicity of species-dependent and external factors. Our objective was to investigate thermal biology of Liolaemus ruibali in a high altitude cold desert at the arid Puna region, Argentina. We address the following question: do sex and seasonal variations in environmental temperature induce changes in the ecophysiological traits? We measured and compared the operative temperatures between fall and spring; and between sexes and seasons, we compared the ecophysiological traits of lizards, microenvironmental temperatures and thermoregulatory behavior. Air and operative temperatures were different between seasons. We found an effect of season-sex interaction on field body temperatures, preferred temperatures, panting threshold and thermal quality. The voluntary and critical temperatures presented seasonal variation in relation to changes in environmental temperatures, suggesting thermal acclimatization. We note behavioral changes between seasons, with the substrate being the main resource for gaining heat in spring. We conclude that Liolaemus ruibali is an efficient thermoregulator; it is a eurythermic lizard and presents phenotypic plasticity in different ecophysiological and behavioral traits induced by sex and seasonality. In addition, we predict that this population could buffer the effects of projected global warming scenarios.
Subject(s)
Altitude , Body Temperature Regulation/physiology , Global Warming , Lizards/physiology , Seasons , Acclimatization , Adaptation, Physiological , Animals , Argentina , Body Temperature , TemperatureABSTRACT
La regulación de la temperatura corporal en las lagartijas juega un rol clave para la supervivencia de las especies. Su condición fisiológica, en referencia a su dependencia de la temperatura ambiente, los convierte en un excelente modelo de estudio. Asimismo, los cambios en el ciclo reproductivo provocan modificaciones en los parámetros termofisiológicos. Este estudio es el primero en abordar la relación de la termorregulación con la actividad reproductiva y el sexo, para una especie de Liolaemus de la ecorregión del Chaco. El objetivo de este trabajo fue determinar cómo influye el período reproductivo, de reclutamiento y el pos-reproductivo, así como también el efecto del sexo y la longitud-hocico-cloaca sobre la termorregulación de Liolaemus chacoensis. Los individuos fueron capturados a mano en el sector Sur de Valle Fértil, provincia de San Juan, Argentina. Se capturaron un total de 44 individuos durante noviembre 2014, febrero 2015 y marzo 2015. Se registró la temperatura corporal (Tc), la temperatura del sustrato (Ts) y del aire (Ta). También, se utilizaron modelos biofísicos para registrar la temperatura operativa. Posteriormente, en el laboratorio se evaluó la temperatura seleccionada (Tsel). Luego se calculó el índice de eficiencia termorregulatoria. Los resultados indicaron que la Tc de L. chacoensis se relacionó positivamente con la Ta, presentando un comportamiento heliotérmico que se mantuvo durante los períodos y el sexo. Asimismo, la Tc fue mayor para el período reproductivo y de reclutamiento con respecto al pos-reproductivo. En particular, solo el sexo tuvo efecto sobre la Tsel, sin embargo para el rango intercuartil de Tsel tuvo efecto tanto el período del ciclo reproductivo como el sexo. El índice de eficiencia termorregulatoria indicó que L. chacoensis es un termoconforme absoluto. Sin embargo, en el período reproductivo tanto machos como hembras cambian hacia la termorregulación activa. Estos resultados muestran que los parámetros termofisiológicos, varían en los diferentes períodos del ciclo reproductivo y la selección activa de micrositios sería un mecanismo para el mantenimiento de la temperatura corporal de la especie.
Thermoregulation of Liolaemus chacoensis lizard (Squamata: Liolaemidae) during its reproductive cycle, in the Western Chaco, Argentina. Regulation of body temperature in lizards plays a key role in the survival of species. Their physiological condition, in reference to their dependence on the ambient temperature makes them an excellent study model. Also, changes in the reproductive cycle cause changes in thermophysiological parameters. This study is the first to address the relationship of thermoregulation with reproductive activity and sex, for a species of Liolaemus from the Chaco ecoregion. The aim of this work was to determine how the reproductive, recruitment and post-reproductive periods influences, as well as the effect of sex and snout-vent length on the thermoregulation of Liolaemus chacoensis. Individuals were captured by hand in the Southern sector of Valle Fertil, San Juan province, Argentina. A total of 44 individuals were captured during the months of November 2014, February 2015 and March 2015. Body (Tb), substrate (Ts) and air (Ta) temperatures were recorded. Also, biophysical models were used to record operative temperatures. Later selected temperatures (Tsel) were evaluated at the laboratory. Finally, thermoregulatory efficiency index was calculated. Results indicated that L. chacoensis Tb was positively related to Ta, presenting a heliothermic behavior that was maintained during periods and sex. Also, Tb was higher in reproductive and recruitment periods than in post-reproductive period. In particular, only sex had an effect on Tsel, however for the interquartile range of Tsel both the period of reproductive cycle and sex had an effect. The thermoregulatory efficiency index indicated that L. chacoensis is an absolute thermoconformist. However, in the reproductive period both males and females change towards active thermoregulation. These results show that thermophysiological parameters vary in different periods of reproductive cycle and the active microsite selection would be a mechanism in maintenance of body temperature of this species.
ABSTRACT
Locomotion is relevant to the ecology of reptiles because of its presumed influence on an organism's Darwinian fitness. Moreover, in ectothermic species, physiological performance capacity is affected by body temperature. We analyzed two components of locomotor performance in three species of lizards, Phymaturus extrilidus, Liolaemus parvus, and Liolaemus ruibali, in the Puna environment of Argentina. First, we estimated the thermal sensitivity of locomotion by measuring sprint speed at four different body temperatures. We included two measures of sprint speed: initial velocity and long sprint for sustained runs. Based on these data, we calculated the optimal temperature for performance and the optimal performance breadth. We also estimated endurance capacity at a single temperature. Maximum sprint speed for L. parvus was greater than L. ruibali and P. extrilidus in both initial velocity and long sprint. In contrast, L. parvus exhibited lower levels of endurance than L. ruibali and P. extrilidus. However, endurance in L. ruibali exceeded that of P. extrilidus. The species differed in the optimal temperature for the initial velocity with the lowest for L. ruibali (31.8 °C) followed by P. extrilidus (33.25 °C) and then L. parvus (36.25 °C). The optimal temperature for long sprint varied between 32 and 36 °C for all species. We found that all species attained maximum performance at body temperatures commonly experienced during daily activity, which was higher than the thermal quality of the environment. We found evidence for thermal sensitivity in locomotor performance in these species. However, we also show that the broad thermal breadth of performance suggests that the lizards are capable of sustaining near optimal levels of locomotor performance at ambient temperatures that would appear to be suboptimal. Thus, this lizard assemblage is capable of coping with the highly variable climatic conditions in the Puna region of Argentina.