Tree composition mitigates the negative effects of urbanization on specialist and generalist forest moth communities

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 benefits of Lepidoptera-rich host trees were
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.