Urbanization alters the landscape, degrades and fragments habitats, and can have a profound effect on species interactions. Plant-pollinator networks may be particularly sensitive to urbanization, because plants and their insect pollinators have been shown to respond to urbanization both positively and negatively. To better understand the relationship between urbanization, pollinator behavior, and season on pollinator-mediated plant reproduction, we created 30 experimental plant populations along an urbanization gradient in the Greater Toronto Area, Canada. To test how urbanization affects plant reproduction and between-patch pollen dispersal, we created a standard hermaphroditic plant patch at each site, and a male-sterile plant patch at a subset of sites. We measured plant reproduction in the early and late summer in each of 2 years. Plants in urban sites produced significantly fewer flowers than plants in the nonurban sites, whereas seed number per plant either increased or decreased with urbanization, depending on the season. Experimental populations in urban sites also exhibited reduced pollen dispersal between patches. Pollen dispersal between patches was greatest early in the summer and declined with increased impervious surface and proximity to the city. Together, our results are likely caused by variation in environmental conditions and pollinator services across the urban gradient, resulting in pollen limitation and pollen dispersal differences among sites. Our work adds to the small but growing body of literature on urban plant-pollinator interactions and suggests that responses to urbanization are context-dependent.

中文翻译：

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传粉媒介介导的植物繁殖在整个城市化梯度中的变化。

城市化改变了地貌，使栖息地退化和破碎，并可能对物种相互作用产生深远影响。植物授粉媒介网络可能对城市化特别敏感，因为已经证明植物及其昆虫授粉媒介对城市化有积极和消极的反应。为了更好地了解城市化，授粉媒介行为和授粉媒介介导的植物繁殖季节之间的关系，我们在加拿大大多伦多地区沿城市化梯度创建了30个实验植物种群。为了测试城市化如何影响植物繁殖和斑块之间的花粉扩散，我们在每个站点创建了一个标准的雌雄同体的植物补丁，并在一部分站点创建了雄性不育的植物补丁。我们测量了两年中初夏和夏末的植物繁殖。城市地区的植物产生的花明显少于非城市地区的植物，而每棵植物的种子数随城市化程度而增加或减少，具体取决于季节。城市地区的实验人群在斑块之间的花粉散布也减少了。夏季初，花粉之间的花粉散布最大，但随着不透水表面和城市距离的增加，花粉的散布量下降。总之，我们的结果很可能是由于环境条件和整个城市梯度上的传粉媒介服务的变化所致，从而导致了花粉限制和站点之间花粉分散的差异。我们的工作增加了关于城市植物与授粉媒介之间相互作用的文献，但文献数量却在不断增长，并表明对城市化的反应取决于环境。