Department of Biology, Indiana University, Bloomington, 47405, IN, USA; Environmental Resilience Institute, Indiana University, Bloomington, 47405, IN, USA.
Department of Biology, Indiana University, Bloomington, 47405, IN, USA.
Environ Pollut. 2021 Jun 15;279:116867. doi: 10.1016/j.envpol.2021.116867. Epub 2021 Mar 17.
In the modern era of industrialization, illuminated nights have become a common defining feature of human-occupied environments, particularly cities. Artificial light at night (ALAN) imposes several known negative impacts on the neuroendocrine system, metabolism, and seasonal reproduction of species living in the wild. However, we know little about the impact of ALAN on populations of birds that either live year-round in the same location or move to different latitudes across seasons. To test whether ALAN has a differing impact on the reproductive timing of bird populations that winter in sympatry but breed at different latitudes, we monitored sedentary and migratory male dark-eyed juncos that were or were not exposed to low intensity (∼2.5 ± 0.5 lux) ALAN. All groups were held in common conditions and day length was gradually increased to mimic natural day length changes (NDL). We assessed seasonal reproductive response from initiation to termination of the breeding cycle. As expected based on earlier research, the sedentary birds exhibited earlier gonadal recrudescence and terminated breeding later than the migratory birds. In addition, resident and migrant birds exposed to ALAN initiated gonadal recrudescence earlier and terminated reproductive events sooner as compared to their conspecifics experiencing NDL. Importantly, the difference in the reproductive timing of sedentary and migratory populations was maintained even when exposed to ALAN. This variation in the seasonal reproductive timing may likely have a genetic basis or be the result of early developmental effects imposed due to different light regimes related to the latitude of origin. This study reveals first that ALAN accelerated reproductive development across both migrants and residents and second that latitude-dependent variation in reproductive timing is maintained despite exposure to ALAN. These results corroborate a relationship between latitude, population, and reproductive timing while also revealing ALAN's impact on seasonal reproductive timing. This study reveals that, ALAN accelerated reproductive development but maintained latitude-dependent variation in reproductive timing across both migrant and resident bird populations.
在现代工业化时代，照明的夜晚已经成为人类居住环境的一个共同特征，尤其是城市。夜间人工照明（ALAN）对生活在野外的物种的神经内分泌系统、代谢和季节性繁殖产生了一些已知的负面影响。然而，我们对那些全年生活在同一地点或在季节迁徙到不同纬度的鸟类种群受 ALAN 影响的情况知之甚少。为了测试 ALAN 是否对在同域越冬但在不同纬度繁殖的鸟类种群的繁殖时间产生不同的影响，我们监测了处于非迁徙状态和迁徙状态的雄性暗眼灯草雀，它们或暴露于低强度（约 2.5±0.5 勒克斯）的 ALAN 下，或未暴露于 ALAN 下。所有组都处于相同的条件下，并且逐渐增加白天的长度以模拟自然的白天长度变化（NDL）。我们从繁殖周期的开始到结束评估季节性繁殖反应。基于早期的研究，我们预期到，非迁徙鸟类的性腺复壮较早，繁殖结束较晚。此外，与经历 NDL 的同种鸟类相比，暴露于 ALAN 下的留鸟和候鸟的性腺复壮更早，生殖事件更早结束。重要的是，即使暴露于 ALAN 下，非迁徙和迁徙种群的繁殖时间差异仍然存在。这种季节性繁殖时间的变化可能具有遗传基础，或者是由于与起源纬度相关的不同光照条件下的早期发育效应所致。这项研究首先揭示了 ALAN 加速了迁徙和留鸟的繁殖发育，其次揭示了尽管暴露于 ALAN 下，繁殖时间的纬度依赖性变化仍然得以维持。这些结果证实了纬度、种群和繁殖时间之间的关系，同时也揭示了 ALAN 对季节性繁殖时间的影响。这项研究揭示了 ALAN 加速了繁殖发育，但维持了迁徙和留鸟种群中依赖纬度的繁殖时间变化。
