Ants in the city: How urban landscapes shape diversity in the southeast

Urbanization is reshaping ecosystems globally, but its effects on biodiversity vary across cities and regions. In high-latitude cities, studies often report neutral or even positive impacts of low-level urbanization on biodiversity, suggesting that urban areas can act as biodiversity reservoirs. Toward the equator, however, urbanization tends to have more negative effects, though the reasons remain unclear—partly due to limited research in low-latitude cities compared to temperate counterparts. To address this gap, we conducted the first survey of insect diversity in Atlanta, Georgia, focusing on ants, to assess urbanization’s impacts in the southeastern U.S.—a biodiversity hotspot relative to northern cities. We examined both direct effects of urbanization (e.g., impervious surface cover, vegetation complexity) and indirect effects via invasive species, which are especially prevalent in southeastern urban areasWe sampled ant communities at 47 sites across three habitat types along a gradient of urban stress: fragmented greenspace (most urban), manicured parks (moderately urban), and forested parks (least urban). Contrary to patterns observed in northern cities, where biodiversity typically declines with increasing urbanization, we found a non-linear pattern: species richness peaked in moderately urban manicured parks and was lower in both highly urban and minimally urban sites. The unexpectedly low diversity in forested parks was associated with the presence of Brachyponera chinensis, the invasive Asian needle ant. These results align with broader latitudinal patterns, suggesting that invasive species may be a primary driver of biodiversity loss in low-latitude cities—raising concerns for conservation in global biodiversity hotspots.