Larson Rachel N, Sander Heather A
Department of Geographical and Sustainability Sciences, University of Iowa, 316 Jessup Hall, Iowa City, IA 52242, United States.
J Mammal. 2024 Oct 24;106(2):339-351. doi: 10.1093/jmammal/gyae121. eCollection 2025 Apr.
Urbanization is a key driver of habitat loss and fragmentation worldwide, yet many urban ecosystems contain vegetated habitat patches that support diverse wildlife communities. Managing urban systems to support robust wildlife communities requires us to understand the mechanisms that drive the response of species to the urban environment. Small mammals are key components of terrestrial ecosystems (e.g., seed predators, prey) and likely also carry out these roles in urban ecosystems; however, the effects of urbanization on small mammal communities are understudied. To identify how species-specific responses to urban environments shape community composition, we quantified both overall community and species-specific changes in small mammal abundance across an urbanization gradient in a Midwestern US metropolitan area. We combined small mammal trapping and land cover data to generate a hierarchical community abundance model. Species diversity increased with increasing proportional cover of human-modified land cover (i.e., impervious surfaces and turfgrass). This finding is driven by high species diversity on sites bordering streams in mowed parks and low diversity on sites with high tree canopy closure. Additionally, modeling results indicated that species responded differently to landscape attributes, leading to variation in small mammal community composition across the urbanization gradient: prairie-associated species tended to be more abundant in tall vegetation bordering mowed parks while habitat generalists tended to be more abundant on sites with greater canopy closure and shrub cover. Our results suggest studies that focus on community-level responses (e.g., species richness) to urbanization may miss important species-specific responses. It may be particularly important to assess both species-specific and community-level responses in cities at ecotones (e.g., between forest and grassland) where species with different habitat requirements may replace one another in different types of green spaces, thereby changing community composition without affecting species diversity or richness. Our findings also indicate that vegetated urban patches, especially patches with tall vegetation cover and low canopy cover, are important habitat for prairie-associated small mammal communities, providing conservation options in heavily altered landscapes.
城市化是全球栖息地丧失和破碎化的关键驱动因素，但许多城市生态系统包含有植被的栖息地斑块，这些斑块支撑着多样的野生动物群落。管理城市系统以支持强大的野生动物群落需要我们了解驱动物种对城市环境做出反应的机制。小型哺乳动物是陆地生态系统的关键组成部分（例如种子捕食者、猎物），在城市生态系统中可能也发挥着这些作用；然而，城市化对小型哺乳动物群落的影响尚未得到充分研究。为了确定物种对城市环境的特定反应如何塑造群落组成，我们在美国中西部大都市地区的城市化梯度上量化了小型哺乳动物总体群落和特定物种丰度的变化。我们将小型哺乳动物诱捕数据和土地覆盖数据相结合，生成了一个分层群落丰度模型。物种多样性随着人类改造土地覆盖（即不透水表面和草坪草）比例的增加而增加。这一发现是由修剪过的公园中靠近溪流的地点的高物种多样性以及树冠郁闭度高的地点的低多样性所驱动的。此外，建模结果表明，物种对景观属性的反应不同，导致小型哺乳动物群落组成在城市化梯度上存在差异：与草原相关的物种在修剪过的公园边缘的高大植被中往往更为丰富，而栖息地通才在树冠郁闭度和灌木覆盖率更高的地点往往更为丰富。我们的结果表明，专注于城市化的群落水平反应（例如物种丰富度）的研究可能会忽略重要的物种特定反应。在生态交错带（例如森林和草原之间）的城市中评估物种特定和群落水平的反应可能尤为重要，在这些地方，具有不同栖息地需求的物种可能在不同类型的绿地中相互取代，从而在不影响物种多样性或丰富度的情况下改变群落组成。我们的研究结果还表明，有植被的城市斑块，特别是植被覆盖率高且树冠覆盖率低的斑块，是与草原相关的小型哺乳动物群落的重要栖息地，为严重改变的景观提供了保护选择。
