Population persistence is informed by the ability of individuals to cope with local abiotic conditions, which is commonly mediated by physiological traits. Among biphasic amphibians, juveniles—which are infrequently studied but play a key role in amphibian population dynamics—are the first life stage to experience terrestrial conditions following the aquatic larval stage. To illuminate phenotypic variation that may allow juveniles to survive the physiological challenges presented by this transition, we examined respiratory surface area water loss (RSAWL) and standard metabolic rates (SMR) among juveniles reared under common larval conditions for five salamander species (Ambystoma annulatum, A. maculatum, A. opacum, A. talpoideum, and A. texanum) collected across ~ 200 km of latitude in Missouri, USA. We found that SMR described 34% of variation in RSAWL, suggesting that physiological water conservation may be limited by energetic regulation among these species, and vice versa. On average, species differed in juvenile SMR and residual values of RSAWL (corrected for body size/shape) by 0.04 mL \({\mathrm{CO}}_{2}\cdot{{\mathrm{g}}^{-1}\cdot \mathrm{hr}}^{-1}\) and 0.16, respectively, possibly because of distinct species ecologies. For example, A. annulatum had higher SMR and RSAWL compared to broadly distributed study species, potentially associated with a relatively narrow range of environmental conditions experienced across the small geographic distribution of A. annulatum. Latitude correlated negatively with temperature and precipitation, and positively with RSAWL, suggesting that variation in RSAWL may be adaptive to local conditions. We provide evidence that species differences likely have a genetic basis, reflecting selection favoring species divergence to effectively use distinct microhabitats.

个体具有应付局部非生物条件的能力，这是种群持久性的标志，这通常是由生理特征介导的。在两栖两栖动物中，很少被研究但在两栖动物种群动态中起关键作用的幼虫是经历水生幼虫阶段后陆生条件的第一个生命阶段。照亮的表型变异，其可以允许青少年生存由该过渡给出的生理挑战，我们检查了呼吸表面积水分损失（RSAWL）和五个蝾螈物种共同幼虫条件下饲养的青少年中标准代谢率（SMR）（Ambystoma annulatum，黄斑曲霉，不透明曲霉，talpoideum和德州曲霉）收集在美国密苏里州的〜200公里纬度上。我们发现SMR描述了RSAWL中34％的变异，这表明生理水保护可能受到这些物种中能量调节的限制，反之亦然。平均而言，物种的青少年SMR和RSAWL的残留值（根据身体大小/形状校正）相差0.04 mL \（{\ mathrm {CO}} _ {2} \ cdot {{\ mathrm {g}} ^ {- 1} \ cdot \ mathrm {hr}} ^ {-1} \）和0.16，可能是由于不同的物种生态。例如，A. annulatum有较高的SMR和RSAWL相比广泛分布研究物种，潜在地具有相对窄的范围内的跨越的较小的地理分布经历的环境条件相关联A. annulatum。纬度与温度和降水呈负相关，与RSAWL呈正相关，这表明RSAWL的变化可能适应于当地条件。我们提供的证据表明，物种差异可能具有遗传基础，反映出有利于物种差异以有效利用独特的微生境的选择。