Thermo-physiological changes and reproductive investment in a liolaemid lizard at the extreme of the slow-fast continuum.

Gravid female lizards often experience reduced thermal preferences and impaired locomotor performance. These changes have been attributed to the physical burden of the clutch, but some authors have suggested that they may be due to physiological adjustments. We compared the thermal biology and locomotor performance of the lizard Liolaemus wiegmannii 1 week before and 1 week after oviposition. We found that gravid females had a thermal preference 1°C lower than that of non-gravid females. This was accompanied by a change in the thermal dependence of maximum running speed. The thermal optimum for locomotor performance was 2.6°C lower before oviposition than after. At relatively low temperatures (22 and 26°C), running speeds of females before oviposition were up to 31% higher than for females after oviposition. However, at temperatures above 26°C, females achieved similar maximum running speeds (∼1.5 m s-1) regardless of reproductive stage. The magnitude of the changes in thermal parameters and locomotor performance of L. wiegmannii females was independent of relative clutch mass (clutches weighed up to 89% of post-oviposition body mass). This suggests that the changes are not simply due to the clutch mass, but are also due to physiological adjustments. Liolaemus wiegmannii females simultaneously adjusted their own physiology in a short period in order to improve locomotor performance and allocated energy for embryonic development during late gravid stage. Our findings have implications for understanding the mechanisms underlying life histories of lizards on the fast extreme of the slow-fast continuum, where physiological exhaustion could play an important role.

Correspondence between thermal biology and locomotor performance in a liolaemid lizard from the southeastern coastal Pampas of Argentina.

The behavioral and physiological mechanisms of thermoregulation and the morphological traits of lizards result in a particular range of body temperatures, which influence performance and ultimately fitness. We studied the thermal biology and locomotor performance of the lizard Liolaemus wiegmannii from the coastal dunes in the southeastern Pampas of Argentina. During the austral summer, we examined the link between thermoregulation and optimal locomotor performance. Liolaemus wiegmannii faced a stressful environment due to high risk of overheating; despite this, the species was able to achieve field body temperatures (Mean Tb ± SD = 35.58 ± 2.86 °C) than expected by chance (i.e., the null model) and suitable for sustaining its physiological performance. Locomotion in this species was thermally-sensitive, with lizards showing high-performance bouts at a relatively wide range of body temperatures (30-38 °C). Lizards exhibited a mean maximum running speed of 1.30 m/s at 37.3 °C (i.e., optimal temperature for locomotion) which was within the set point range of preferred temperature (Tset = 35.4-37.5 °C). Therefore, we found a correspondence between thermal optimum and preferred temperature. Our findings suggest that L. wiegmannii, like other lizard species with a broad distribution, is capable of performing well across a wide range of temperatures despite the spatiotemporal thermal fluctuations of the environment.

Latitudinal pattern of the thermal sensitivity of running speed in the endemic lizard Liolaemus multimaculatus.

Physiological performance in lizards may be affected by climate across latitudinal or altitudinal gradients. In the coastal dune barriers in central-eastern Argentina, the annual maximum environmental temperature decreases up to 2°C from low to high latitudes, while the mean relative humidity of the air decreases from 50% to 25%. Liolaemus multimaculatus, a lizard in the family Liolaemidae, is restricted to these coastal dunes. We investigated the locomotor performance of the species at 6 different sites distributed throughout its range in these dune barriers. We inquired whether locomotor performance metrics were sensitive to the thermal regime attributable to latitude. The thermal performance breadth increased from 7% to 82% with latitude, due to a decrease in its critical thermal minimum of up to 5°C at higher latitudes. Lizards from high latitude sites showed a thermal optimum, that is, the body temperature at which maximum speed is achieved, up to 4°C lower than that of lizards from the low latitude. At relatively low temperatures, the maximum running speed of high-latitude individuals was faster than that of low-latitude ones. Thermal parameters of locomotor performance were labile, decreasing as a function of latitude. These results show populations of L. multimaculatus adjust thermal physiology to cope with local climatic variations. This suggests that thermal sensitivity responds to the magnitude of latitudinal fluctuations in environmental temperature.

Latitudinal comparison of the thermal biology in the endemic lizard Liolaemus multimaculatus.

Thermoregulation in ectotherms may be modulated by climatic variability across geographic gradients. Environmental temperature varies along latitudinal clines resulting in heterogeneous thermal resource availability, which generally induces ectotherms to use compensatory mechanisms to thermoregulate. Lizards can accommodate to ambient temperature changes through a combination of adaptive evolution and behavioral and physiological plasticity. We studied the thermal ecology of the endangered endemic lizard Liolaemus multimaculatus at six different sites distributed from the northern to southern areas of the distribution (700 km) in the Atlantic dune barriers of Argentina, and even including the borders areas of the distribution range. Environmental temperatures and relative humidity showed a strong contrast between northern and southern limits of the distribution range. The northern localities had operative temperatures (Te) above the range of preferred temperatures (Tset), instead, the southern localities had large proportion of Tes within the Tset. Although these different climatic conditions may constrain the thermal biology of L. multimaculatus, individuals from all localities maintained relatively similar field body temperatures (XTb = 34.07 ± 3.02 °C), suggesting that this parameter is conservative. Thermal preference partially reflected latitudinal temperature gradient, since lizards from the two southernmost localities showed the lowest Tsel and Tset. Thermoregulatory efficiency differed among localities, since E values in the northern localities (E = 0.53-0.69) showed less variability than those of southern localities (E = 0.14-0.67). Although L. multimaculatus employed a strategy of having a conservative Tb and being able to acclimatize the thermal preference to copes with latitudinal changes in the thermal environment, other local factors, such as ecological interactions, may also impose limitations to thermoregulation and this may interfered in the interpretation of results at wider spatial scale.

A new species of the Liolaemus alticolor-bibronii group (Iguania: Liolaemidae) from East-central Argentina.

We describe a new species of Liolaemus of the L. alticolor-bibronii group of the subgenus Liolaemus sensu stricto. We studied meristic, morphometric and qualitative pattern characters. Statistical tests were performed in order to evaluate morphological differences among the candidate species and the most closely geographically distributed species. Molecular analyses of Cyt-b mitochondrial gene were performed in order to estimate the position of the new species in relation to other taxa. We also recorded natural history data such as habitat, behavior, reproductive state, diet, and body temperature. Liolaemus absconditus sp. nov. differs from other species of Liolaemus in presenting a distinct combination of morphological character states of lepidosis and color pattern, being phylogenetically close to Liolaemus tandiliensis, Liolaemus gracilis and Liolaemus saxatilis. The new species is a saxicolous and endemic lizard of the Tandilia Mountain Range System of Buenos Aires Province.

Seasonal shifts in the thermal biology of the lizard Liolaemus tandiliensis (Squamata, Liolaemidae).

Small lizards can accommodate to constraints imposed by temporal changes in ambient temperature through a combination of adaptive evolution and behavioral and physiological plasticity. Thermal physiology plasticity may compensate for climate variation and favor performance while minimizing behavioral costs in sub-optimal conditions. The Tandilia's lizard, Liolaemus tandiliensis, occurs in an isolated mountain range of the Argentinean temperate Pampas. In this study, we compared the thermal biology of L. tandiliensis between late spring (December) and mid-summer (February). The habitats' thermal quality was lower in late spring than in mid-summer. The lizard's field-body temperature (Tb) was 2-3 °C higher than the operative temperature (Te). Overall, the mean preferred temperature (Tsel) was 37.4 °C [preferred range (Tset): 36.2-38.7 °C], and was similar to other Liolaemus species. The Tset and Tsel of females in late spring were 1.8 °C lower than in mid-summer. In the case of males, the Tsel did not vary among seasons, while the Tset had a difference of 2.5 °C between seasons. Adults were moderate thermoregulators, but females were more efficient only in late spring (Emales = 0.69; Efemales = 0.58), compared to mid-summer (Emales = 0.68; Efemales = 0.50). Juveniles did not show temporal differences in temperature preferences and had a relatively higher efficiency in late spring (E = 0.38) compared to mid-summer (E = 0.28). An increased proportion of juveniles and adults shifted their Tb near to the Tset in late spring respect to mid-summer. The adults also matched their preferred temperatures to their current body temperature. These results suggest that seasonal shifts in the thermoregulatory parameters of L. tandiliensis may improve their thermoregulatory efficiency. Although temporal variation in ambient temperatures might influence the thermal biology of the studied lizards, other factors such as changes in the reproductive status may have also interfered.

Scale dependency of Liolaemus lizards' home range in response to different environmental variables.

Animal habitat-use patterns cannot be isolated from scale issues. Consequently, multi-scale studies provide a complete characterization of ecological patterns that can further explain the observed variation. Liolaemus constitutes the world's second most speciose lizard genus. In this study, we assessed the relationships between home range size and environmental variables at 3 different spatial scales. The study at a local and regional scale was focused on the habitat specialist Liolaemus multimaculatus. The lizard's home range was calculated using the minimum convex polygon method in populations from grassland sites of the coastal sand dunes of the Argentinean Pampas under 2 different conditions, with or without forestations of Acacia longifolia. On the other hand, at a geographical scale we considered the evolutionary implications of 20 species of Liolaemus. Home range size, phylogeny, ecological, environmental, and climatic data were obtained from the literature and remote sensing. L. multimaculatus home range varied from 12.66 to 570.00 m. Regionally, this species had smaller home ranges in forested habitats ([Formula: see text]: 94.02 m2) compared with the non-forested sites ([Formula: see text]: 219.78 m2). Habitat structure, vegetation types, and food availability would explain the space use at finer scales. When the 20 species of Liolaemus were considered, high mean air temperature and broad thermal amplitudes showed an inverse relationship with home range size. Neither net primary productivity nor phylogeny was good predictors for home range variation at geographical scale. This study highlights the scale dependence of the explicative capability of a set of environmental and intrinsic variables on home range patterns.