Distance from buildings affects ant communities: native or invasive?

Urban ecosystems lead to biological homogenization through habitat degradation and support of invasive species. Invasive ants are known to have a complex negative impact on their new ecosystem, mainly on other ant species. As ants are an important component of natural ecosystems, this may have substantial consequences on many other organisms. I studied the effect of disturbance on ant communities over an urban-rural gradient in the San Francisco Bay, California. My main hypothesis was that invasive ant species have an advantage at disturbed habitats, while native species have an advantage in preserved habitats. I sampled ants in 12 sites along the gradient, in addition to various environmental factors, including distance from buildings, paved and unpaved roads, water source, and irrigation; land use cover, etc. The preliminary results show major differences between ant communities along a gradient of human disturbance. In the pristine native habitats, which are remote from disturbance, only native ant species were found. On the other end of the gradient, in similar habitats that are closer to buildings, roads, and irrigation, most native species are displaced by invasive ones. In an RDA analysis, the invasive species were separated from the native ones according to their distance from buildings, which was the most important disturbance factor found. Four invasive ant species were found in the mostly disturbed sites. The invasive species thrive in the urban environment, exploiting the excessive availability of food and water. However, even in the middle of a heavily disturbed habitat, some pockets of native species are still present.