Tree composition mitigates the negative effects of urbanization on specialist and generalist forest moth communities.
Abstract
Changes at local and landscape scales impact forests embedded in urban and urbanizing landscapes. In the Northeast USA, urban forest fragments are characterized by smaller sizes, low connectivity and novel plant assemblages relative to intact natural areas. Disruptions of connectivity from landscape-scale development can negatively impact habitat suitability and colonization by terrestrial insects, but managing local tree compositions may offset negative impacts, especially for phytophagous taxa specialized to host plants. Here, we surveyed nocturnal moth community diversity using light traps deployed within forest fragments that varied in surrounding urban development, tree floristics, and tree structure. We found that local and landscape-scale factors interact to affect temperate forest moth communities. In most cases, impervious surface (as a proxy for urbanization) negatively impacted moth communities, whereas the basal area of Lepidoptera-rich host plants positively affected moth communities. However, the magnitude of the benefits of Lepidoptera-rich host trees was most apparent at low levels of urbanization and most substantial for specialists over generalists. Practical implication. These results provide evidence that forest management approaches prioritizing tree species that support a high richness of species interactions can offset the adverse effects of fragmentation on vital insect taxa at different levels of urban development. However, at high levels of urban development, other urban-associated mechanisms, such as artificial light, pesticides, and reduced dispersal, may inhibit sustainable populations of sensitive moth species.