Climate change has shifted geographical ranges of species northwards or to higher altitudes on elevational gradients. These changes have been associated with increases in ambient temperatures. For ectotherms in seasonal environments, however, life history theory relies largely on the length of summer, which varies somewhat independently of ambient temperature per se. Extension of summer reduces seasonal time constraints and enables species to establish in new areas as a result of over-wintering stage reaching in due time. The reduction of time constraints is also predicted to prolong organisms' breeding season when reproductive potential is under selection. We studied temporal change in the summer length and its effect on species' performance by combining long-term data on the occurrence and abundance of nocturnal moths with weather conditions in a boreal location at Värriötunturi fell in NE Finland. We found that summers have lengthened on average 5 days per decade from the late 1970s, profoundly due to increasing delays in the onset of winters. Moth abundance increased with increasing season length a year before. Most of the species occurrences expanded upwards in elevation. Moth communities in low elevation pine heath forest and middle elevation mountain birch forest have become inseparable. Yet, the flight periods have remained unchanged, probably due to unpredictable variation in proximate conditions (weather) that hinders life histories from selection. We conclude that climate change-driven changes in the season length have potential to affect species' ranges and affect the structure of insect assemblages, which may contribute to alteration of ecosystem-level processes.

中文翻译：

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气候变化驱动的北方夜蛾间的海拔变化。

气候变化使物种的地理范围向北移动，或随着海拔梯度向更高的高度移动。这些变化与环境温度的升高有关。但是，对于季节性环境中的外热而言，生活史理论在很大程度上取决于夏季的长短，夏季的长短与环境本身的温度无关。延长夏季减少了季节性的时间限制，并使物种由于在适当的时候达到了越冬阶段而在新的地区定居。时间限制的减少还预测，以延长生物的繁殖季节，生殖能力正在选择。我们研究了夏季长度的时间变化及其对物种的影响 在芬兰东北部Värriötunturi的一个寒带地区，结合夜间飞蛾的发生和丰度与天气状况的长期数据，从而获得更好的性能。我们发现，从1970年代后期开始，夏季平均每十年延长5天，这很大程度上是由于冬季开始延迟的缘故。蛾的数量随着一年前季节长度的增加而增加。大多数物种的出现都在海拔高度上扩展。低海拔松树荒漠林和中海拔山白桦林的蛾类群落已经密不可分。然而，飞行时间保持不变，这可能是由于临近状况（天气）发生了无法预测的变化，从而阻碍了人们选择生命史。我们得出结论，气候变化驱动的季节长度变化可能会影响物种的