Parallel evolution on a global scale

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.

城市化以重塑自然环境的方式改变生物演化进程。我们通过在全球160座城市的6169个种群中采集110019株白车轴草样本，探究城市环境变化是否会驱动平行演化。我们对这些植株开展了孟德尔式抗草食防御性状的检测，该性状同时也会影响植株对非生物胁迫的耐受性。全球范围内有47%的城市中，城乡环境梯度与防御性状渐变群的演化存在关联。不同城市间干旱胁迫与植被覆盖的环境变化，可解释渐变群强度的差异。对来自26座城市的2074个基因组进行测序后发现，城乡渐变群的演化最符合适应性演化的解释，但平行适应的程度在不同城市间存在差异。本研究结果证实，城市化可在全球尺度上驱动生物适应性演化。