Urbanization has opposing effects on the trophic niche of three ubiquitous soil animal taxa

Soil microarthropods comprise diverse trophic groups and contribute to many soil functions, including carbon and nutrient cycling. However, there is comparatively little known about how these organisms and their trophic ecologies respond to urbanization. In this study, we tested whether urbanization constrains trophic niches in three representative microarthropod taxa (Collembola, Oribatida, and Mesostigmata) across an established urbanization gradient in Rochester, New York, USA. We used stable isotope analysis (δ¹³C, δ¹⁵N) as a tool to study this phenomenon, and we found that δ¹³C and δ¹³N shifted slightly within and between the microarthopod taxa in response to urbanization. However, we saw more stark contrast between these taxa groups when we compared isotopic niche space between the taxa, and found that Oribatida and Collembola experienced a diminishment in their isotope niche area. In contrast, Mesostigmata experienced an expansion in their niche area as a result of urbanization. Collectively, these findings underscore that microarthropod taxa respond uniquely to urbanization depending on their underlying biology and ecology, and the trophic niche of some organisms may even be enlarged by urbanization pressures. Thus, our study highlights the need to further understand the link between soil animal community composition, function, and the facilitation of soil ecosystem services in urban areas.