Straka Tanja M, Radchuk Viktoriia, Kowarik Ingo, von der Lippe Moritz, Buchholz Sascha
Department of Ecology Technische Universität Berlin Berlin Germany.
Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB) Berlin Germany.
Ecol Evol. 2025 Jan 11;15(1):e70791. doi: 10.1002/ece3.70791. eCollection 2025 Jan.
Urbanization as a major driver of global change modifies biodiversity patterns and the abundance and interactions among species or functional species groups. For example, urbanization can negatively impact both predator-prey and mutualistic relationships. However, empirical studies on how urbanization modifies biotic, particularly multitrophic, interactions are still limited. In this study, we applied a framework focused on a predator-prey-mutualistic relationship involving communities of insect-pollinated vascular plants, pollinators (bees and hoverflies), predatory spiders, and sand lizards as top predators to test (i) the effect of urbanization on abundance and species richness at different trophic levels and (ii) the effect of urbanization on the regulation of biotic interactions using correlations between species abundances as a proxy. By assessing 56 dry grassland patches in Berlin, Germany, we found that higher trophic levels (sand lizard abundance as well as predatory spider species richness and abundance) were significantly impacted by urbanization whereas pollinators were affected to a lesser degree (only abundance, but not species richness). In contrast, insect-pollinated vascular plants were not impacted by urbanization. Path analyses revealed significant relationships in low-urbanized areas. In these areas, we observed significant bottom-up-regulated mutualistic and predator-prey interactions (plants-pollinators, and pollinators-predatory spiders), as well as top-down-regulated predator-prey interactions (sand lizards-pollinators, and predatory spiders-pollinators). In contrast, no significant interactions were found in highly urbanized sites. Our results suggest that bottom-up regulation is stronger than top-down regulation in low-urbanized areas. To our knowledge, this is the first study to examine the effects of urbanization on predator-prey-mutualistic interactions and to determine whether these interactions are regulated by bottom-up or top-down processes. These findings enhance our understanding of multitrophic interactions in urban environments and their associated ecosystem services, such as pollination, thereby supporting efforts in urban biodiversity conservation.
城市化作为全球变化的主要驱动力，改变了生物多样性模式以及物种或功能物种组之间的丰度和相互作用。例如，城市化会对捕食者 - 猎物关系和互利关系产生负面影响。然而，关于城市化如何改变生物相互作用，特别是多营养级相互作用的实证研究仍然有限。在本研究中，我们应用了一个框架，该框架聚焦于涉及昆虫授粉维管植物群落、传粉者（蜜蜂和食蚜蝇）、捕食性蜘蛛以及作为顶级捕食者的沙蜥的捕食者 - 猎物 - 互利关系，以测试（i）城市化对不同营养级的丰度和物种丰富度的影响，以及（ii）城市化对生物相互作用调节的影响，使用物种丰度之间的相关性作为代理。通过评估德国柏林的56个干草原斑块，我们发现较高营养级（沙蜥丰度以及捕食性蜘蛛物种丰富度和丰度）受到城市化的显著影响，而传粉者受到的影响较小（仅丰度，而非物种丰富度）。相比之下，昆虫授粉维管植物未受城市化影响。路径分析揭示了低城市化地区存在显著关系。在这些地区，我们观察到显著的自下而上调节的互利和捕食者 - 猎物相互作用（植物 - 传粉者，以及传粉者 - 捕食性蜘蛛），以及自上而下调节的捕食者 - 猎物相互作用（沙蜥 - 传粉者，以及捕食性蜘蛛 - 传粉者）。相比之下，在高度城市化的地点未发现显著相互作用。我们的结果表明，在低城市化地区，自下而上的调节比自上而下的调节更强。据我们所知，这是第一项研究城市化对捕食者 - 猎物 - 互利相互作用的影响，并确定这些相互作用是由自下而上还是自上而下过程调节的研究。这些发现增进了我们对城市环境中多营养级相互作用及其相关生态系统服务（如授粉）的理解，从而支持城市生物多样性保护工作。
