Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada.
Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON, L5L 1C6, Canada.
Sci Rep. 2023 Nov 22;13(1):20437. doi: 10.1038/s41598-023-47524-8.
Urbanization is altering landscapes globally at an unprecedented rate. While ecological differences between urban and rural environments often promote phenotypic divergence among populations, it is unclear to what degree these trait differences arise from genetic divergence as opposed to phenotypic plasticity. Furthermore, little is known about how specific landscape elements, such as green corridors, impact genetic divergence in urban environments. We tested the hypotheses that: (1) urbanization, and (2) proximity to an urban green corridor influence genetic divergence in common milkweed (Asclepias syriaca) populations for phenotypic traits. Using seeds from 52 populations along three urban-to-rural subtransects in the Greater Toronto Area, Canada, one of which followed a green corridor, we grew ~ 1000 plants in a common garden setup and measured > 20 ecologically-important traits associated with plant defense/damage, reproduction, and growth over four years. We found significant heritable variation for nine traits within common milkweed populations and weak phenotypic divergence among populations. However, neither urbanization nor an urban green corridor influenced genetic divergence in individual traits or multivariate phenotype. These findings contrast with the expanding literature demonstrating that urbanization promotes rapid evolutionary change and offer preliminary insights into the eco-evolutionary role of green corridors in urban environments.
城市化正在以前所未有的速度改变着全球的景观。虽然城市和农村环境之间的生态差异通常会促进种群之间表型的分异，但尚不清楚这些性状差异是源于遗传分化还是表型可塑性。此外，人们对于特定的景观元素（如绿色走廊）如何影响城市环境中的遗传分化知之甚少。我们检验了以下假设：（1）城市化，以及（2）接近城市绿色走廊是否会影响常见乳草（Asclepias syriaca）种群的表型性状的遗传分化。我们从加拿大大多伦多地区的三条从城市到农村的亚截线的 52 个种群中采集种子，其中一个种群沿着绿色走廊，我们在一个共同的花园中种植了大约 1000 株植物，并在四年内测量了与植物防御/损伤、繁殖和生长相关的 20 多个重要生态特征。我们发现常见乳草种群内有 9 个性状具有显著的遗传变异性，并且种群间的表型分化较弱。然而，城市化和城市绿色走廊都没有影响单个性状或多变量表型的遗传分化。这些发现与越来越多的表明城市化促进快速进化变化的文献相矛盾，并为绿色走廊在城市环境中的生态进化作用提供了初步的见解。
