Effects of Acute and Chronic Environmental Disturbances on Lizards of Patagonia

Effects of blood extraction and ecophysiological experiments on stress in adult males of Liolaemus attenboroughi

Stress during laboratory experiments can affect the outcomes of ecophysiological studies. The serum corticosterone concentration (CORT), the leukocyte profile, heterophil/lymphocyte ratio (H/L), and the presence of blood endoparasites were analyzed as a proxy of stress and immunological state in adult males of the lizard Liolaemus attenboroughi, endemic to Patagonia, Argentina. The results of the ecophysiological variables (preferred temperature, running speed, locomotor endurance, and body condition index, BCI) were analyzed in relation to stress indicators obtained from blood samples taken at three different times: at capture, and on the third and seventh days in the laboratory. Males at capture showed a high percentage of lymphocytes and heterophils and a low of basophils, monocytes, and eosinophils. Haemogregorina-type endoparasites have been recorded in the genus Liolaemus for the first time. The proportion of infected males remained stable during captivity; however, these males showed higher CORT levels, increased percentages of basophils, and decreased percentages of lymphocytes. There was a significant increment in CORT and H/L, and a decrease in BCI during laboratory experiments, compared with baseline values at capture. The performance was not related to the CORT or the repeated blood sampling. The BCI decreased, possibly due to energy reserve mobilization caused by acute stress. This study shows that blood extraction and ecophysiological experiments over 7 days have a minor effect on the stress indicators used.

Looking at the past to infer into the future: Thermal traits track environmental change in Liolaemidae

The diversity of habitats generated by the Andes uplift resulted a mosaic of heterogeneous environments in South America for species to evolve a variety of ecological and physiological specializations. Species in the lizard family Liolaemidae occupy a myriad of habitats in the Andes. Here, we analyze the tempo and mode of evolution in the thermal biology of liolaemids. We assessed whether there is evidence of local adaptation (lability) or conservatism (stasis) in thermal traits. We tested the hypothesis that abiotic factors (e.g., geography, climate) rather than intrinsic factors (egg-laying [oviparous] or live-bearing [viviparous], substrate affinity) explain variation in field active body temperature (T_b ), preferred temperature (T_p ), hours of restriction of activity, and potential hours of activity. Although most traits exhibited high phylogenetic signal, we found variation in thermal biology was shaped by geography, climate, and ecological diversity. Ancestral character reconstruction showed shifts in T_b tracked environmental change in the past ∼20,000 years. Thermal preference is 3°C higher than T_b , yet exhibited a lower rate of evolution than T_b and air temperature. Viviparous Liolaemus have lower T_b s than oviparous species, whereas T_p is high for both modes of reproduction, a key difference that results in a thermal buffer for viviparous species to cope with global warming. The rapid increase in environmental temperatures expected in the next 50-80 years in combination with anthropogenic loss of habitats are projected to cause extirpations and extinctions in oviparous species.

Thermal biology and locomotor performance in Phymaturus calcogaster: are Patagonian lizards vulnerable to climate change?

Behavioral and physiological traits of ectotherms are especially sensitive to fluctuations of environmental temperature. In particular, niche-specialist lizards are dependent on their physiological plasticity to adjust to changing environmental conditions. Lizards of the genus Phymaturus are viviparous, mainly herbivorous, and inhabit only rock promontories in the steppe environments of Patagonia and the Andes. Herein, we examine the vulnerability of the southernmost Phymaturus species to global warming: the endemic Phymaturus calcogaster, which lives in a mesic environment in eastern Patagonia. We studied body temperatures in the field (T_b ), preferred body temperatures in a thermogradient (T_pref ), the operative (T_e ) and environmental temperatures, and the dependence of running performance on body temperature. P. calcogaster had a mean T_b (27.04°C) and a mean T_e (31.15°C) both lower than their preferred temperature (T_pref = 36.61°C) and the optimal temperature for running performance (T_o = 37.13°C). Lizard activity seems to be restraint during the early afternoon due high environmental temperatures. However, both, the high safety margin and warming tolerance suggest that the expected increase in environmental temperatures due to global warming (IPCC report in 2018) would not threaten, but indeed enhance locomotor performance in this population.

Decrease in preferred temperature in response to an immune challenge in lizards from cold environments in Patagonia, Argentina

In ectotherms, the likelihood of surviving an infection is determined by the efficiency of thermoregulation, the availability of a variety of thermal microenvironments, the individual's health status, and the virulence of the infective agent. Physiological and behavioral demands related to an efficient immune response entail a series of costs that compete with other vital activities, specifically energy storage, growth, reproduction, and maintenance functions. Here, we characterize the thermal biology and health status by the presence of injuries, ectoparasites, body condition, and individual immune response capacity (using phytohemagglutinin in a skin-swelling assay) of the southernmost lizards of the world, Liolaemus sarmientoi, endemic to a sub-optimal, cold environment in Patagonia, Argentina. In particular, we study the effect of a bacterial endotoxin (lipopolysaccharide; LPS-treatment) on thermoregulation. We found that the field-active body temperature (T_b) was much lower than the preferred body temperature (T_p) obtained in the laboratory. All the individuals were in good body condition at the beginning of the experiments. The phytohemagglutinin test caused detectable thickening in sole-pads at 2 h and 24 h post-assay in males and non-pregnant females, indicating a significant innate immune response. In the experimental immune challenge, the individuals tended to prefer a low body temperature after LPS-treatment (2 h post-injection) and developed hypothermia, while the control individuals injected with phosphate buffered saline (PBS), maintained their body temperature throughout the trial. In both the LPS-treatment and PBS-control individuals, BC declined during the experiment. Hypothermia may allow this southernmost species to optimize the use of their energetic resources and reduce the costs of thermoregulation in a cold-temperate environment where they rarely attain the mean T_p (35.16 °C) obtained in laboratory.