Resource partitioning in a snake assemblage from east-central Argentina

Physiological thermal responses of three Mexican snakes with distinct lifestyles

The impact of temperature on reptile physiology has been examined through two main parameters: locomotor performance and metabolic rates. Among reptiles, different species may respond to environmental temperatures in distinct ways, depending on their thermal sensitivity. Such variation can be linked to the ecological lifestyle of the species and needs to be taken into consideration when assessing the thermal influence on physiology. This is particularly relevant for snakes, which are a very functionally diverse group. In this study, our aim was to analyze the thermal sensitivity of locomotor performance and resting metabolic rate (RMR) in three snake species from central Mexico (Crotalus polystictus, Conopsis lineata, and Thamnophis melanogaster), highlighting how it is influenced by their distinctive behavioral and ecological traits. We tested both physiological parameters in five thermal treatments: 15 °C, 25 °C, 30 °C, 33 °C, and 36 °C. Using the performance data, we developed thermal performance curves (TPCs) for each species and analyzed the RMR data using generalized linear mixed models. The optimal temperature for locomotion of C. polystictus falls near its critical thermal maximum, suggesting that it can maintain performance at high temperatures but with a narrow thermal safety margin. T. melanogaster exhibited the fastest swimming speeds and the highest mass-adjusted RMR. This aligns with our expectations since it is an active forager, a high energy demand mode. The three species have a wide performance breadth, which suggests that they are thermal generalists that can maintain performance over a wide interval of temperatures. This can be beneficial to C. lineata in its cold habitat, since such a characteristic has been found to allow some species to maintain adequate performance levels in suboptimal temperatures. RMR increased along with temperature, but the proportional surge was not uniform since thermal sensitivity measured through Q10 increased at the low and high thermal treatments. High Q10 at low temperatures could be an adaptation to maintain favorable performance in suboptimal temperatures, whereas high Q10 at high temperatures could facilitate physiological responses to heat stress. Overall, our results show different physiological adaptations of the three species to the environments they inhabit. Their different activity patterns and foraging habits are closely linked to these adaptations. Further studies of other populations with different climatic conditions would provide valuable information to complement our current understanding of the effect of environmental properties on snake physiology.

An annotated list of the reptiles of the highland grassland of Tandilia Mountains, Argentina

The study of biodiversity is a fundamental step to develop conservation strategies. Reptile populations are immersed in a global crisis, due to anthropic disturbances. Almost the entire Pampa ecoregion in Argentina was modified for agricultural and livestock activities, the only remnants of mountain native grasslands in Buenos Aires province being the Tandilia and Ventania mountain systems. Ventania reptiles have been exhaustively researched in last years, while Tandilia counts with fewer studies. We presented an actualized reptiles list of the Tandilia Mountain System. We used five data sources to collect presence records: literature, fieldwork, museum collection, citizen science, and a online database. The composition of reptiles from the Tandilia Mountain range includes 26 species in 12 families. Due to the presence of several endemic reptiles, and the representativeness of more than half of the reptiles of Pampa Ecoregion, Tandilia would be useful to determine conservation priority areas to conserve the native grassland and their reptile fauna.