Data from: Temperature niche shift observed in a Lepidoptera population under allochronic divergence

A process of adaptive divergence for tolerance to high temperatures was identified by using a rare model-system, consisting of two sympatric populations of a Lepidoptera (Thaumetopoea pityocampa) with different life-cycle timings, a "mutant" population with summer larval development, Leiria SP, and the founder natural population, having winter larval development, Leiria WP. A third, allopatric population (Bordeaux WP) was also studied. First and second instar larvae were experimentally exposed to daily-cycles of heat treatment reaching maximum values of 36, 38, 40 and 42ºC; control groups placed at 25ºC. A lethal temperature effect was only significant at 42ºC, for Leiria SP, whereas all temperatures tested had a significant negative effect upon Leiria WP, thus indicating an upper threshold of survival c.a. 6ºC above that of the WP. Cox regression model, for pooled heat treatments, predicted mortality hazard to increase for Leiria WP (+108%) and Bordeaux WP (+78%) in contrast with Leiria SP; to increase by 24% for each additional ºC; and to decrease by 53% from first to second instar larvae. High variability among individuals was observed, a population characteristic that may favour selection and consequent adaptation. Present findings provide an example of ecological differentiation, following a process of allochronic divergence. Results further contribute to a better understanding of the implications of climate change for ecological genetics.本研究采用一套罕见的模式系统，鉴定出一类针对高温耐受的适应性分化过程。该系统包含两种同域分布的鳞翅目（Lepidoptera）松异舟蛾（Thaumetopoea pityocampa）种群，二者生活周期节律存在显著差异：其一为夏季幼虫发育的‘突变’种群Leiria SP，其二为保留冬季幼虫发育特性的奠基自然种群Leiria WP。此外本研究还对第三个异域种群波尔多WP（Bordeaux WP）开展了研究。研究人员将1龄与2龄幼虫置于每日循环的高温处理环境中进行胁迫实验，处理最高温度分别设置为36℃、38℃、40℃及42℃，对照组幼虫则饲养于25℃环境下。结果表明，仅当处理温度为42℃时，Leiria SP种群才表现出显著的致死温度效应；而所有测试温度均对Leiria WP种群产生了显著的负面影响，提示其生存上限阈值较WP种群高出约6℃。针对合并后的高温处理数据集构建Cox回归模型（Cox regression model），结果显示：相较于Leiria SP种群，Leiria WP种群与Bordeaux WP种群的死亡风险分别上升108%与78%；温度每升高1℃，个体死亡风险提升24%；与1龄幼虫相比，2龄幼虫的死亡风险降低53%。本研究观察到种群内个体间存在较高的表型变异度，这一特征可能有利于自然选择作用的发生及后续的适应性演化。本研究结果为异时分化（allochronic divergence）后的生态分化提供了典型实例，同时也为深入理解气候变化对生态遗传学的影响提供了新的科学依据。