Comparative thermal ecophysiology in Pristidactylus scapulatus populations from the Puna region of Argentina.

Reptiles are important models for understanding fundamental aspects of physiological ecology and for assessing how environmental change can impact biodiversity. Abiotic factors (micro-environmental temperatures, operative temperatures, thermal quality) may vary geographically along an altitudinal and latitudinal gradient, and therefore the different thermal resources available for thermoregulation also vary. Comparative analyses among populations provide an opportunity to understand how variation in abiotic factors can affect different ecophysiological traits of a species at different geographical points. Our objective was to carry out a comparative study between two populations of Pristidactylus scapulatus in the Puna region of Argentina, providing the first data available on thermal ecophysiology, thermoregulatory efficiency and locomotor performance of the species. We determined field body temperature, micro-environmental temperatures and operative temperatures. In the laboratory, we measured preferred temperatures and calculated the index of thermoregulatory efficiency. In addition, we recorded critical temperature (minimum and maximum) and we estimated the thermal sensitivity of locomotion by measuring sprint speed at different body temperatures; based on these data we calculated the optimal temperature for performance, the optimal performance breadth and thermal safety margin. Air temperatures and operative temperatures were different between sites. However, we only found differences between populations in the minimum critical temperatures, with these being lower at higher latitude. We note that P. scapulatus populations adjust optimal temperatures of performance to field body temperatures and preferred temperatures, which could reduce the costs of thermoregulation in lizards with limited daily activity and who inhabit sites with variable and unpredictable environment temperatures. We conclude that Pristidactylus scapulatus has thermal sensitivity in locomotor performance, is a moderate thermoregulator with respect to the environment and is a eurithermic lizard, which has thermal flexibility in the cold.

Exploring the effects of warming seas by using the optimal and pejus temperatures of the embryo of three Octopoda species in the Gulf of Mexico.

Using data related to thermal optimal and pejus of the embryos of Octopus americanus from Brazil and O. insularis and O. maya from Mexico, this study aimed to project the potential distribution areas in the Gulf of Mexico and predict distribution shifts under different Representative Concentration Pathway scenarios (RCP 6 and 8.5) for the years 2050 and 2100. The different thermal tolerances elicited different responses to current and future scenarios. In this sense, O. insularis and O. maya thermal niches stretch from the Caribbean to Florida. Nevertheless, O. insularis may inhabit warmer areas than O. maya. Surprisingly, no area was considered thermally habitable for O. americanus, which could have been associated with the use of data of populations thermally adapted to temperate conditions south of Brazil. According to models, a warming scenario would cause a restriction of the available thermal niche of O. maya, while O. insularis could expand under RCP 6 scenarios. This restriction was more substantial in the RCP 8.5 scenario. Nevertheless, under the RCP 8.5 scenario, the temperature in 2100 may negatively affect even O. insularis, the species most thermal tolerant. If our results are accurate, the fishing yield of O. insularis will increase in the future, replacing the heavily exploited O. maya in the coasts of the southern Gulf of Mexico. Regarding O. americanus, no inference might be made until thermal tolerances of locally adapted populations can be studied.

Effect of temperature on the locomotor performance of species in a lizard assemblage in the Puna region of Argentina.

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.