Data from: Living in the city: urban environments shape the evolution of a native annual plant

Urban environments are warmer, have higher levels of atmospheric CO2, and altered patterns of disturbance and precipitation than nearby rural areas. These differences can be important for plant growth and are likely to create distinct selective environments. We planted a common garden experiment with seeds collected from natural populations of the native annual plant Lepidium virginicum, growing in five urban and nearby rural areas in the northern United States to determine whether and how urban populations differ from those from surrounding rural areas. When grown in a common environment, plants grown from seeds collected from urban areas bolted sooner, grew larger, had fewer leaves, had an extended time between bolting and flowering, and produced more seeds than plants grown from seeds collected from rural areas. Interestingly, the rural populations exhibited larger phenotypic differences from one another than urban populations. Surprisingly, genomic data revealed that the majority of individuals in each of the urban populations were more closely related to individuals from other urban populations than they were to geographically proximate rural areas – the one exception being urban and rural populations from New York which were nearly identical. Taken together our results suggest that selection in urban environments favors different traits than selection in rural environments and that these differences can drive adaptation and shape population structure.

与周边乡村区域相比，城市环境温度更高、大气二氧化碳（CO₂）浓度更大，且干扰模式与降水格局均发生改变。这类差异对植物生长具有重要影响，并可能塑造出独特的选择环境。我们以采集自美国北部5个城市及周边乡村区域的本土一年生植物北美独行菜（Lepidium virginicum）自然种群的种子为材料，开展了同质园实验（common garden experiment），以明确城市种群与周边乡村种群是否存在差异以及差异产生的机制。在同质环境下培养时，相较于乡村种群来源的植株，城市种群来源的植株抽薹更早、植株体量更大、叶片数量更少，抽薹至开花的间隔时长更长，且结籽量更多。值得注意的是，乡村种群间的表型差异相较于城市种群更为显著。令人意外的是，基因组数据分析显示，各城市种群中的绝大多数个体与其他城市种群的个体亲缘关系，相较于与地理邻近的乡村种群的亲缘关系更近——仅纽约州的城乡种群是例外，二者几乎完全一致。综合以上结果，我们认为城市环境中的选择作用与乡村环境所青睐的性状存在差异，且这类差异可推动适应性演化并塑造种群结构。