Urban structures are poor stepping stones for crevice-nesting ants in fragmented landscapes

Abstract

Despite the high fragmentation of its natural habitats—grasslands with limestone rocks—a previous study revealed that the ant species Temnothorax nigriceps show no evidence of genetic isolation between populations separated by kilometers of presumably unsuitable landscape. In the present study, we hypothesized that urban anthropogenic structures might allow the species to nest and maintain efficient gene flow in spite of the ongoing fragmentation. To test this, we surveyed the presence of T. nigriceps in many putatively suitable anthropized habitats—such as stone walls, ornamental devices, or urban park structures—in an urban area near a continuous source of propagules from natural habitats. We found very few occurrences of T. nigriceps in this urban area, suggesting either a low density of nests in such habitats or difficulty in detecting them in anthropized environment. We discuss the importance of surrounding vegetation and water sources for nesting, especially in anthropized environment where temperatures on mineral surfaces can exceed those in the species’ natural habitats. We conclude that T. nigriceps tend to nest in the most natural-like structures, implying that urban habitats provide poor substitute for the species’ native environment.