Dominoni Davide M, Van't Hof Thomas J, Partecke Jesko
Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G128QQ, UK; Department of Migration and Immuno-ecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany; Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
Takizaki Corporation, 2-4-7 Honkomagome, Bunkyo-ku, Tokyo 113-0021, Japan.
Physiol Behav. 2015 Apr 1;142:14-9. doi: 10.1016/j.physbeh.2015.01.026. Epub 2015 Jan 22.
Despite urban ecology being an established field of research, there is still surprisingly little information about the relative contribution of specific environmental factors driving the observed changes in the behavior and physiology of city dwellers. One of the most reported effects of urbanization is the advanced phenology observed in birds. Many factors have been suggested to underline such effect, including warmer microclimate, anthropogenic food supply and light pollution. Since social stimuli are known to affect reproductive timing and breeding density is usually higher in urban populations compared to rural ones, we experimentally tested whether social interactions could advance the onset of reproduction in European blackbirds (Turdus merula). We housed male blackbirds of rural and urban origins with or without a conspecific female, and recorded their seasonal variation in gonadal size and production of luteinizing hormone (LH). Paired and unpaired males of both urban and rural origins did not significantly differ in their timing of gonadal growth. Moreover, rural and urban birds did not differ in their response to the social stimuli, rather they became reproductively active at the same time, a result that confirms previous studies that attributed the difference in reproductive timing observed in the field to phenotypic plasticity. We conclude that social stimuli do not contribute substantially to the observed early onset of reproductive physiology in urban bird species, rather other factors such as light pollution are likely to be stronger drivers of these physiological changes.
尽管城市生态学已是一个既定的研究领域，但令人惊讶的是，关于驱动城市居民行为和生理变化的特定环境因素的相对贡献，仍知之甚少。城市化最常被报道的影响之一是鸟类物候提前。许多因素被认为是这种影响的潜在原因，包括更温暖的微气候、人为食物供应和光污染。由于已知社会刺激会影响繁殖时间，而且城市种群的繁殖密度通常高于农村种群，我们通过实验测试了社会互动是否会使欧乌鸫（Turdus merula）的繁殖开始提前。我们将来自农村和城市的雄性乌鸫与同种雌性一起或单独饲养，并记录它们性腺大小和促黄体生成素（LH）分泌的季节性变化。来自城市和农村的成对和不成对雄性在性腺发育时间上没有显著差异。此外，农村和城市的鸟类对社会刺激的反应没有差异，而是同时进入繁殖活跃期，这一结果证实了之前的研究，即把在野外观察到的繁殖时间差异归因于表型可塑性。我们得出结论，社会刺激对城市鸟类物种中观察到的繁殖生理提前开始没有实质性贡献，其他因素如光污染可能是这些生理变化的更强驱动因素。
