Department of Ecology and Genetics, University of Oulu, Oulu, Finland.
Present address: Department of Forest Sciences, University of Helsinki, 00014 Helsinki, Finland.
J Biol Rhythms. 2022 Oct;37(5):516-527. doi: 10.1177/07487304221108968. Epub 2022 Aug 3.
Photoperiodic reproductive diapause is an essential part of female life cycle in several insect species living on high latitudes, where overwintering in reproductive stage involves high risks for survival and progeny production. The sensitive period (SP), during which photoperiodic cues can trigger the switch from direct development to diapause, can last from a few hours or days after emergence to the entire life span of females. Moreover, in some species, sexually mature females can enter post-reproductive diapause as a response to decreasing day length and/or temperature. We studied the duration of SP for diapause induction and the females' ability to enter post-reproductive diapause at short day lengths in strains from different latitudes in Europe, North America, and Japan. Our study shows that the females of this species have a life-long SP and that they retain an ability to switch between reproduction and diapause as a response to back-and-forth changes in day length for at least 3 months. strains from different latitudes showed high variation in females' ability to enter post-reproductive diapause; females of the southern strains generally requiring longer time and/or lower temperature to enter this stage than those of the northern strains. Moreover, the proportion of females that switched to post-reproductive diapause in 3 weeks in short day conditions at 16 °C showed positive correlation with the critical day length (CDL) for diapause induction and the latitudinal and continental origin of the strains. Life-long SP increases females' flexibility to respond to short-term changes in environmental conditions and enables reproducing females to switch to post-reproductive diapause when the days get shorter and colder toward the autumn. This ability can play a major role in species phenology and should be taken into account in theoretical and empirical studies on insect adaptation to seasonal variation.
光周期生殖滞育是生活在高纬度地区的几种昆虫物种雌性生命周期的重要组成部分，在生殖阶段越冬涉及到生存和后代繁殖的高风险。敏感期（SP）是指光周期线索可以触发从直接发育到滞育转变的时期，它可以从羽化后几个小时或几天持续到雌性的整个寿命。此外，在一些物种中，性成熟的雌性可以进入产后滞育，以响应日长和/或温度的下降。我们研究了不同纬度的欧洲、北美和日本的品系在短日照条件下诱导滞育的 SP 持续时间和雌性进入产后滞育的能力。我们的研究表明，该物种的雌性具有终生的 SP，并且它们保留了一种在日长来回变化时在繁殖和滞育之间切换的能力，至少可以持续 3 个月。来自不同纬度的品系在雌性进入产后滞育的能力方面表现出高度的变异性；通常，来自南方的品系的雌性进入这个阶段需要更长的时间和/或更低的温度，而来自北方的品系的雌性则不需要。此外，在 16°C 的短日照条件下，3 周内有多少雌性转变为产后滞育与滞育诱导的临界日长（CDL）以及品系的纬度和大陆起源呈正相关。终生的 SP 增加了雌性对环境条件短期变化的灵活性，并使繁殖雌性在向秋季过渡时，当日长变短、天气变冷时，能够转变为产后滞育。这种能力在物种物候学中起着重要作用，在昆虫对季节性变化的适应的理论和实证研究中应予以考虑。
