Thermophysiological plasticity could buffer the effects of global warming on a Patagonian lizard.

Ecophysiological plasticity determines, to a great extent, the geographic distribution and the vulnerability of ectotherms to climate change. We studied the relationship between locomotor performance and temperature of Liolaemus elongatus lizards in three populations in northern Patagonia, Argentina, differing in thermal characteristics. We related the thermophysiological and locomotor performance parameters with the environmental conditions currently experienced by these populations and analyzed whether the expected increment of the environmental temperature due to climate change could affect these vital traits. We also determined, for one of the populations, the effects of 30 acclimation days at two temperature treatments (22°C and 30°C) on running speed, thermal preference in the laboratory (Tpref ), panting threshold, and minimum critical temperature. We found that L. elongatus, despite the differences in environmental temperatures among the three sites, exhibited maximum speed at similar temperatures (optimum temperature for locomotor performance; To ). The southern populations currently experience temperatures below that required to reach their maximum locomotor performance while the northernmost population is threatened by peaks of high temperatures that exceed the To . Therefore, global warming could diminish lizards' running performance in northern populations and lizards may spend more time refuging and less time on other activities such as feeding, territory defense, and dispersion. However, we show evidence of plasticity in L. elongatus locomotor performance when acclimated at high temperatures resulting in a potential advantage to cushion the effect of the rising environmental temperatures expected during climate change.

Potential benefits from global warming to the thermal biology and locomotor performance of an endangered Patagonian lizard.

Global warming can significantly affect many aspects of the biology of animal species, including their thermal physiology and physiological performance. Thermal performance curves provide a heuristic model to evaluate the impacts of temperature on the ecophysiology of ectotherms. When integrated with other thermal biology parameters, they can be used to predict the impacts of climate change on individual fitness and population viability. In this study, we combine holistic measures of thermal physiology and the thermal sensitivity of locomotor performance with environmental temperatures measured at fine scale to estimate the vulnerability to global warming of the endangered Patagonian lizard Phymaturus tenebrosus. Our results indicate that this lizard exhibits its preferred temperatures and maximum locomotor performance at higher temperatures than the mean temperature it currently experiences in its habitat. In addition, it exhibits a low effectiveness of thermoregulation, being a poor thermoregulator. In view of the results obtained, we suggest that the climatic conditions of Patagonia may be advantageous for P. tenebrosus to survive future global warming, since its thermal physiology and locomotor performance may improve under increasing in environmental temperatures in its habitat.

Reproductive strategies in males of the world's southernmost lizards.

Reproductive and life history patterns in reptiles are tightly related to the environmental conditions, so male reproductive cycles have been historically characterized as continuous, for tropical lizards, or seasonal, for temperate lizards. However, males of Liolaemus and Phymaturus lizards (Liolaemidae), from cold temperate climates of high altitudes or latitudes in Argentina and Chile, have developed a variety of reproductive cycles to coordinate with the short female reproductive season and to deal with the low frequency of reproductive females in the population. Using gonadal histology and morphological analysis, we describe the male reproductive biology, fat storage and sexual dimorphism of the viviparous lizards Liolaemus sarmientoi and Liolaemus magellanicus that inhabit an austral grass steppe at 51°S, in the southern limit of the American continent. Males of L. sarmientoi and L. magellanicus are reproductively available during the entire activity season of approximately 5 months. In addition, males of both species exhibit greater body sizes than females in morphological variables relevant in sexual selection. Meanwhile, females of both species exhibit larger inter-limb length than conspecific males, which suggests fecundity selection to increase space for a larger litter size. The continuous sperm production throughout the activity season allows these liolaemids to mate at any time when females ovulate, representing a selective advantage to deal with the short activity season and the adversities of the cold environment they inhabit.