Data from: Hotter nests produce hatchling lizards with lower thermal tolerance

In many regions, the frequency and duration of summer heatwaves is predicted to increase in future. Hotter summers could result in higher temperatures inside lizard nests, potentially exposing embryos to thermally stressful conditions during development. Potentially, developmentally plastic shifts in thermal tolerance could allow lizards to adapt to climate warming. To determine how higher nest temperatures affect the thermal tolerance of hatchling geckos, we incubated eggs of the rock-dwelling velvet gecko, Amalosia lesueurii, at two fluctuating temperature regimes to mimic current nest temperatures (mean 23.2°C, range 10–33°C, ‘cold’) and future nest temperatures (mean 27.0°C, range 14–37°C, ‘hot’). Hatchlings from the hot incubation group hatched 27 days earlier and had a lower critical thermal maximum (CTmax 38.7°C) and a higher critical thermal minimum (CTmin 6.2°C) than hatchlings from cold incubation group (40.2 and 5.7°C, respectively). In the field, hatchlings typically settle under rocks near communal nests. During the hatching period, rock temperatures ranged from 13 to 59°C, and regularly exceeded the CTmax of both hot- and cold-incubated hatchlings. Because rock temperatures were so high, the heat tolerance of lizards had little effect on their ability to exploit rocks as retreat sites. Instead, the timing of hatching dictated whether lizards could exploit rocks as retreat sites; that is, cold-incubated lizards that hatched later encountered less thermally stressful environments than earlier hatching hot-incubated lizards. In conclusion, we found no evidence that CTmax can shift upwards in response to higher incubation temperatures, suggesting that hotter summers may increase the vulnerability of lizards to climate warming.未来，全球诸多地区夏季热浪的发生频率与持续时长预计将有所增加。夏季气温升高可能导致蜥蜴巢穴内温度上升，进而可能使胚胎在发育过程中暴露于热胁迫环境之中。理论上，热耐受能力的发育可塑性变化或可帮助蜥蜴适应气候变暖。为探明巢穴温度升高如何影响幼体守宫的热耐受能力，本研究以栖息于岩石生境的莱氏绒守宫（Amalosia lesueurii）的卵为实验材料，设置两种波动温度处理组以模拟当前与未来的巢穴温度：「低温组」平均温度23.2℃，温度范围10–33℃；「高温组」平均温度27.0℃，温度范围14–37℃。相较于低温孵化组的幼体（临界最高热耐受温度（critical thermal maximum, CTmax）为40.2℃、临界最低热耐受温度（critical thermal minimum, CTmin）为5.7℃），高温孵化组的幼体提前27天破壳，且其临界最高热耐受温度（CTmax 38.7℃）更低、临界最低热耐受温度（CTmin 6.2℃）更高。野外环境中，幼体守宫通常栖息于公共巢穴附近的岩石下方。在孵化期内，岩石温度介于13℃至59℃之间，且时常超过高温、低温两组孵化幼体的临界最高热耐受温度。由于岩石温度极高，蜥蜴的热耐受能力对其利用岩石作为躲避场所的能力几乎无影响。反之，破壳时间才是决定蜥蜴能否利用岩石作为躲避场所的关键因素：即较晚破壳的低温孵化组幼体，相较于较早破壳的高温孵化组幼体，所处环境的热胁迫程度更低。综上，本研究未发现临界最高热耐受温度可随孵化温度升高而上调的证据，这表明夏季气温升高或会加剧蜥蜴面临气候变暖时的生存脆弱性。