23Environmental temperatures are a major constraint on ectotherm abundance and 24 diversity, influencing their distribution and natural history. Comparing thermal 25 tolerances with environmental temperatures is a simple way to estimate thermal 26 constraints on species distributions. We investigate the potential effects of thermal 27 tolerance on anuran local (habitat) and global distribution patterns and associated 28 behavioral responses. We tested for differences in Voluntary Thermal Maximum of two 29 sympatric frog species of the genus Physalaemus in the Cerrado ecoregion. For each 30 species, we constructed models to assess the effects of period of day, duration of 31 experiment, initial body mass, initial body temperature and heating rate on the VT Max .
32We mapped the difference between VT Max and maximum daily temperature (VT Max -33 ET Max ) for each occurrence point. Physalaemus nattereri had a significantly higher 34 VT Max than P. cuvieri. For P. nattereri, the model including only period of day was 35 chosen as the best to explain variation in the VT Max . For P. cuvieri, no model was 36 selected as best to predict VT Max . The VT Max -ET Max values were significantly different 37 between species, with P. nattereri mostly found in localities that attain maximum 38 temperatures lower than its VT Max and P. cuvieri showing the reverse pattern. Regarding 39 habitat use, we found P. cuvieri to be slightly more abundant in open habitats than in 40 non-open habitats, whereas P. nattereri shows the reverse pattern. The difference in 41 VT Max values between these two species might be related to their different body sizes, 42 but additionally might reflect their natural history, especially the way they use their 43 habitats, and phylogenetic constraints (the species studied are in different clades within 44 Physalaemus). Our study indicates that differences in behavioral thermal tolerance may 45 be important in shaping local and regional distribution patterns. Furthermore, small-46 3 scale habitat use might reveal a link between behavioral thermal tolerance and natural 47 history strategies. 48 49 50 Environmental temperatures are a major constraint on ectotherm abundance and 51 diversity, influencing their distribution and natural history [1, 2, 3]. Several studies have 52 explored environmental constraints on ectothermic vertebrates at regional and global 53 scale [4, 5, 6]. The physiological performance of individuals can be negatively affected 54 by high environmental temperatures [7], which can lead to declining populations and/or 55 local extinctions [3]. Thus, knowing species thermal tolerance and exploring how 56 environmental temperatures might affect their physiology and restrict their distribution 57is of primary concern for long-term conservation, especially under a global warming 58 trend (e.g. [8]).
59Many studies infer potential distribution of species using solely environmental 60 temperatures from occurrence localities to model their potential niche (e.g. [9-10]).
61However, incorporati...