Does behavioral thermal tolerance predict distribution pattern and habitat use in two sympatric Neotropical frogs?

Environmental temperatures are a major constraint on ectotherm abundance, influencing their distribution and natural history. Comparing thermal tolerances with environmental temperatures is a simple way to estimate thermal constraints on species distributions. We investigate the potential effects of behavioral thermal tolerance (i. e. Voluntary Thermal Maximum, VTMax) on anuran local (habitat) and regional distribution patterns and associated behavioral responses. We tested for differences in Voluntary Thermal Maximum (VTMax) of two sympatric frog species of the genusPhysalaemusin the Cerrado. We mapped the difference between VT(Max)and maximum daily temperature (VTMax-ETMax) and compared the abundance in open and non-open habitats for both species.Physalaemus nattererihad a significantly higher VT(Max)thanP.cuvieri. ForP.nattereri, the model including only period of day was chosen as the best to explain variation in the VT(Max)while forP.cuvieri, the null model was the best model. At the regional scale, VTMax-ET(Max)values were significantly different between species, withP.nattererimostly found in localities with maximum temperatures below its VT(Max)andP.cuvierishowing the reverse pattern. Regarding habitat use,P.cuvieriwas in general more abundant in open than in non-open habitats, whereasP.nattereriwas similarly abundant in these habitats. This difference seems to reflect their distribution patterns:P.cuvieriis more abundant in open and warmer habitats and occurs mostly in warmer areas in relation to its VTMax, whereasP.nattereritends to be abundant in both open and non-open (and cooler) areas and occurs mostly in cooler areas regarding its VTMax. Our study indicates that differences in behavioral thermal tolerance may be important in shaping local and regional distribution patterns. Furthermore, small-scale habitat use might reveal a link between behavioral thermal tolerance and natural history strategies.