Department of Biology, Hobart and William Smith Colleges, 300 Pulteney Street, Geneva, NY, 14456, USA.
Department of Environmental Biology, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY, 13210, USA.
Sci Rep. 2022 Feb 2;12(1):1752. doi: 10.1038/s41598-022-05746-2.
Urbanization is the dominant trend of global land use change. The replicated nature of environmental change associated with urbanization should drive parallel evolution, yet insight into the repeatability of evolutionary processes in urban areas has been limited by a lack of multi-city studies. Here we leverage community science data on coat color in > 60,000 eastern gray squirrels (Sciurus carolinensis) across 43 North American cities to test for parallel clines in melanism, a genetically based trait associated with thermoregulation and crypsis. We show the prevalence of melanism was positively associated with urbanization as measured by impervious cover. Urban-rural clines in melanism were strongest in the largest cities with extensive forest cover and weakest or absent in cities with warmer winter temperatures, where thermal selection likely limits the prevalence of melanism. Our results suggest that novel traits can evolve in a highly repeatable manner among urban areas, modified by factors intrinsic to individual cities, including their size, land cover, and climate.
城市化是全球土地利用变化的主导趋势。与城市化相关的环境变化的可复制性应该会推动平行进化，但由于缺乏多城市研究，城市地区进化过程的可重复性的洞察力一直受到限制。在这里，我们利用社区科学数据，对 43 个北美的 6 万多只东部灰松鼠（Sciurus carolinensis）的毛色进行了研究，以检验黑化这一与体温调节和保护色有关的遗传特征是否存在平行渐变。我们发现，黑化的普遍性与不透水覆盖物所衡量的城市化程度呈正相关。在森林覆盖面积大的大城市中，城市-农村间的黑化渐变最强，而在冬季温度较高的城市中，这种渐变较弱或不存在，因为热选择可能限制了黑化的普遍性。我们的研究结果表明，新的特征可以在城市地区以高度可重复的方式进化，受城市自身内在因素的影响，包括城市的规模、土地覆盖和气候。
