How will climate change impact fossorial lizard species? Two examples in the Baja California Peninsula

Hot, dry, and salty: The present and future of an Extremophile model lizard from Argentina

Global warming poses a threat to lizard populations by raising ambient temperatures above historical norms and reducing thermoregulation opportunities. Whereas the reptile fauna of desert systems is relatively well studied, the lizard fauna of saline environments has not received much attention and-to our knowledge-thermal ecology and the effects of global warming on lizards from saline environments have not been yet addressed. This pioneer study investigates the thermal ecology, locomotor performance and potential effects of climate warming on Liolaemus ditadai, a lizard endemic to one of the largest salt flats on Earth. We sampled L. ditadai using traps and active searches along its known distribution, as well as in other areas within Salinas Grandes and Salinas de Ambargasta, where the species had not been previously recorded. Using ensemble models (GAM, MARS, RandomForest), we modeled climatically suitable habitats for L. ditadai in the present and under a pessimistic future scenario (SSP585, 2070). L. ditadai emerges as an efficient thermoregulator, tolerating temperatures near its upper thermal limits. Our ecophysiological model suggests that available activity hours predict its distribution, and the projected temperature increase due to global climate change should minimally impact its persistence or may even have a positive effect on suitable thermal habitat. However, this theoretical increase in habitat could be linked to the distribution of halophilous scrub in the future. Our surveys reveal widespread distribution along the borders of Salinas Grandes and Salinas de Ambargasta, suggesting a potential presence along the entire border of both salt plains wherever halophytic vegetation exists. Optimistic model results, extended distribution, and no evidence of flood-related adverse effects offer insights into assessing the conservation status of L. ditadai, making it and the Salinas Grandes system suitable models for studying lizard ecophysiology in largely unknown saline environments.

Modelling the effects of climate and land-cover changes on the potential distribution and landscape connectivity of three earth snakes (Genus Conopsis, Günther 1858) in central Mexico

Anthropogenic land use and climate change are the greatest threats to biodiversity, especially for many globally endangered reptile species. Earth snakes (Conopsis spp.) are a poorly studied group endemic to Mexico. They have limited dispersal abilities and specialized niches, making them particularly vulnerable to anthropogenic threats. Species distribution models (SDMs) were used to assess how future climate and land-cover change scenarios might influence the distribution and habitat connectivity of three earth snakes: Conopsis biserialis (Taylor and Smith), C. lineata (Kennicott), and C. nasus (Günther). Two climate models, CNRM-CM5 (CN) and MPI-ESM-LR (MP) (Representative Concentration Pathway 85), were explored with ENMeval Maxent modelling. Important SDM environmental variables and environmental niche overlap between species were also examined. We found that C. biserialis and C. lineata were restricted by maximum temperatures whereas C. nasus was restricted by minimum ones and was more tolerant to arid vegetation. C. biserialis and C. lineata were primarily distributed in the valleys and mountains of the highlands of the TMBV, while C. nasus was mainly distributed in the Altiplano Sur (Zacatecano-Potosino). C. lineata had the smallest potential distribution and suffered the greatest contraction in the future whereas C. nasus was the least affected species in future scenarios. The Sierra de las Cruces and the Sierra Chichinautzin were identified as very important areas for connectivity. Our results suggest that C. lineata may be the most vulnerable of the three species to anthropogenic and climate changes whereas C. nasus seems to be less affected by global warming than the other species.

There and back again: A meta-analytical approach on the influence of acclimation and altitude in the upper thermal tolerance of amphibians and reptiles

Realistic predictions about the impacts of climate change onbiodiversity requires gathering ecophysiological data and the critical thermal maxima (CTMax) is the most frequently used index to assess the thermal vulnerability of species. In the present study, we performed a systematic review to understand how acclimation and altitude affect CTMax estimates for amphibian and non-avian reptile species. We retrieved CTMax data for anurans, salamanders, lizards, snakes, and turtles/terrapins. Data allowed to perform a multilevel random effects meta-analysis to answer how acclimation temperature affect CTMax of Anura, Caudata, and Squamata and also meta-regressions to assess the influence of altitude on CTMax of frogs and lizards. Acclimation temperature influenced CTMax estimates of tadpoles, adult anurans, salamanders, and lizards, but not of froglets. In general, the increase in acclimation temperature led to higher CTMax values. Altitudinal bioclimatic gradient had an inverse effect for estimating the CTMax of lizards and anuran amphibians. For lizards, CTMax was positively influenced by the mean temperature of the wettest quarter. For anurans, the relationship is inverse; we recover a trend of decreasing CTMax when max temperature of warmest month and precipitation seasonality increase. There is an urgent need for studies to investigate the thermal tolerance of subsampled groups or even for which we do not have any information such as Gymnophiona, Serpentes, Amphisbaena, and Testudines. Broader phylogenetic coverage is mandatory for more accurate analyses of macroecological and evolutionary patterns for thermal tolerance indices as CTMax.

Climate-associated decline of body condition in a fossorial salamander

Temperate ectotherms have responded to recent environmental change, likely due to the direct and indirect effects of temperature on key life cycle events. Yet, a substantial number of ectotherms are fossorial, spending the vast majority of their lives in subterranean microhabitats that are assumed to be buffered against environmental change. Here, we examine whether seasonal climatic conditions influence body condition (a measure of general health and vigor), reproductive output, and breeding phenology in a northern population of fossorial salamander (Spotted Salamander, Ambystoma maculatum). We found that breeding body condition declined over a 12-year monitoring period (2008-2019) with warmer summer and autumn temperatures at least partly responsible for the observed decline in body condition. Our findings are consistent with the hypothesis that elevated metabolism drives the negative association between temperature and condition. Population-level reproduction, assessed via egg mass counts, showed high interannual variation and was weakly influenced by autumn temperatures. Salamander breeding phenology was strongly correlated with lake ice melt but showed no long-term temporal trend (1986-2019). Climatic warming in the region, which has been and is forecasted to be strongest in the summer and autumn, is predicted to lead to a 5%-27% decline in salamander body condition under realistic near-future climate scenarios. Although the subterranean environment offers a thermal buffer, the observed decline in condition and relatively strong effect of summer temperature on body condition suggest that fossorial salamanders are sensitive to the effects of a warming climate. Given the diversity of fossorial taxa, heightened attention to the vulnerability of subterranean microhabitat refugia and their inhabitants is warranted amid global climatic change.

Diversity and conservation of terrestrial vertebrates (birds, mammals, and reptiles) of Sierra Cucapá, Mexicali, Baja California, Mexico

Knowledge about the biodiversity of Baja California has been obtained mainly from natural protected areas (NPAs), while some unprotected natural areas have been poorly studied. The Sierra Cucapá in the northeast of the peninsula is one example. The objectives of this study are 1) to integrate existing knowledge of bird, mammal, and reptile diversity in Cucapá from public databases, citizen science platforms, and information generated from fieldwork, 2) to identify the spatial distribution of records in the study area, 3) to compare the composition of vertebrate species of Cucapá with that of NPAs of northern part of the peninsula, and 4) to assess the biological conservation value of Cucapá. We obtained records of 150 species of native vertebrates (102 birds, 34 mammals, and 14 reptiles) of which 10 species of birds, four mammals, and seven reptiles are included in a risk extinction category. The different sources of information contributed in a complementary way to the species inventories. Large areas in western and northern Cucapá lack records. The total difference in species composition between Cucapá and nearby NPAs ranged between 58 and 69% for birds, 61 and 79% for mammals, and 69 and 87% for reptiles. The species richness of Cucapá, its particular species composition, the presence of species in risk extinction categories, and the number and size of unexplored areas indicate that this area represents an opportunity for biological conservation in the northern part of the Peninsula. This work provides compelling data for the protection of Cucapá.

Effect of climate change on the potential distribution of Helodermaalvarezi (Squamata, Helodermatidae)

Climate change represents a real threat to biodiversity conservation worldwide. Although the effects on several species of conservation priority are known, comprehensive information about the impact of climate change on reptile populations is lacking. In the present study, we analyze outcomes on the potential distribution of the black beaded lizard (Helodermaalvarezi Bogert & Martin del Campo, 1956) under global warming scenarios. Its potential distribution, at present and in projections for the years 2050 and 2070, under both optimistic and pessimistic climate change forecasts, were computed using current data records and seven bioclimatic variables. General results predict a shift in the future potential distribution of H.alvarezi due to temperature increase. The optimistic scenario (4.5 W/m²) for 2070 suggests an enlargement in the species' distribution as a response to the availability of new areas of suitable habitat. On the contrary, the worst-case scenario (7 W/m²) shows a distribution decrease by 65%. Moreover, the range distribution of H.alvarezi is directly related to the human footprint, which consequently could magnify negative outcomes for this species. Our research elucidates the importance of conservation strategies to prevent the extinction of the black beaded lizard, especially considering that this species is highly threatened by aversive hunting.

Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

Thermal biology research compares field with laboratory data to elucidate the evolution of temperature-sensitive traits in ectotherms. The hidden challenge of many of these studies is discerning whether animals actively thermoregulate, since motivation is not typically assessed. By studying the behaviours involved in thermoregulation, we can better understand the mechanisms underlying body temperature control. Using an integrative approach, we assessed the thermoregulatory and thermotactic behaviours of two sympatric snake species with contrasting life histories: the generalist Eastern Garter Snake (Thamnophis sirtalis sirtalis ( Linnaeus, 1758 )) and the semi-fossorial Northern Red-bellied Snake (Storeria occipitomaculata occipitomaculata ( Storer, 1839 )). We expected that thermoregulatory behaviours would be optimized based on life history, in that T. s. sirtalis would show higher evidence for thermally oriented behaviours than S. o. occipitomaculata due to its active nature. Thamnophis sirtalis sirtalis actively thermoregulated, had higher thermal preferences (29.4 ± 2.5 vs. 25.3 ± 3.6 °C), and was more active than S. o. occipitomaculata, which showed relatively low evidence for thermotaxis. Our results build on the notion that evaluating movement patterns and rostral orientation towards a heat source can help ascertain whether animals make thermally motivated choices. Our data provide insight into the thermoregulatory strategies used by snakes with different life histories and maximize the information provided by behavioural thermoregulation experiments.