Department of Biology, Lund University, Lund, Sweden.
School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK.
J Anim Ecol. 2023 Oct;92(10):1924-1936. doi: 10.1111/1365-2656.13982. Epub 2023 Aug 13.
Urbanisation is accelerating across the globe, transforming landscapes, presenting organisms with novel challenges, shaping phenotypes and impacting fitness. Urban individuals are claimed to have duller carotenoid-based colouration, compared to their non-urban counterparts, the so-called 'urban dullness' phenomenon. However, at the intraspecific level, this generalisation is surprisingly inconsistent and often based on comparisons of single urban/non-urban populations or studies from a limited geographical area. Here, we combine correlational, experimental and meta-analytical data on a common songbird, the great tit Parus major, to investigate carotenoid-based plumage colouration in urban and forest populations across Europe. We find that, as predicted, urban individuals are paler than forest individuals, although there are large population-specific differences in the magnitude of the urban-forest contrast in colouration. Using one focal region (Malmö, Sweden), we reveal population-specific processes behind plumage colouration differences, which are unlikely to be the result of genetic or early-life conditions, but instead a consequence of environmental factors acting after fledging. Finally, our meta-analysis indicates that the urban dullness phenomenon is well established in the literature, for great tits, with consistent changes in carotenoid-based plumage traits, particularly carotenoid chroma, in response to anthropogenic disturbances. Overall, our results provide evidence for uniformity in the 'urban dullness' phenomenon but also highlight that the magnitude of the effect on colouration depends on local urban characteristics. Future long-term replicated studies, covering a wider range of species and feeding guilds, will be essential to further our understanding of the eco-evolutionary implications of this phenomenon.
城市化正在全球范围内加速，改变景观，给生物带来新的挑战，塑造表型并影响适应性。与非城市个体相比，城市个体据称具有较暗的基于类胡萝卜素的颜色，即所谓的“城市暗淡”现象。然而，在种内水平上，这种概括出人意料地不一致，并且通常基于对单个城市/非城市种群的比较或来自有限地理区域的研究。在这里，我们结合了关于普通鸣禽大山雀 Parus major 的相关性、实验和荟萃分析数据，以调查欧洲城市和森林种群中基于类胡萝卜素的羽毛颜色。我们发现，正如预测的那样，城市个体比森林个体更苍白，尽管在颜色的城市-森林对比的幅度上存在很大的种群特异性差异。使用一个焦点区域（瑞典马尔默），我们揭示了羽毛颜色差异背后的种群特异性过程，这些过程不太可能是遗传或早期生活条件的结果，而是在离巢后环境因素作用的结果。最后，我们的荟萃分析表明，“城市暗淡”现象在大山雀的文献中已经得到很好的证实，与人为干扰有关的基于类胡萝卜素的羽毛特征，特别是类胡萝卜素色度，发生了一致的变化。总体而言，我们的研究结果为“城市暗淡”现象的一致性提供了证据，但也强调了这种现象对颜色的影响程度取决于当地的城市特征。未来的长期重复研究，涵盖更广泛的物种和摄食群体，对于进一步了解这种现象的生态进化意义至关重要。
