Differences in the community composition of nocturnal Lepidoptera between native and invaded forests are linked to the habitat structure

Non-native invasive plants are among the main threats to global biodiversity, including insects, and it is thus important to understand the mechanisms of how invasive plants impact native species. The community composition of nocturnal Lepidoptera was studied in the Czech Republic (Central Europe) in stands of native deciduous trees and in stands dominated by the invasive tree Robinia pseudoacacia, using automatic portable light traps together with an assessment of habitat characteristics. Native stands had more closed canopies and poorly developed understories. Conversely, R. pseudoacacia stands were more open and heterogeneous, with sparse canopies, well-developed shrub layers and a higher cover of taller herbs. Moth species richness, abundance and biomass were lower in R. pseudoacacia, likely due to the low richness of canopy herbivores not adapted to feed on the exotic host. However, feeding guilds associated with the understorey were more represented in stands of R. pseudoacacia, likely due to the more heterogeneous habitat structure. The Lepidopteran communities observed in stands of R. pseudoacacia resembled communities of open-forests or forest-steppe habitats. In contrast, native stands were dominated by Lepidoptera associated with trees, including forest specialists but also habitat generalists. From a conservation perspective, it appears that the invasive R. pseudoacacia created structurally more heterogeneous environment and more Lepidopteran open-forest guilds were associated with this habitat. However, further spread of R. pseudoacacia should be prevented because it reduces the species richness of Lepidoptera. Simultaneously, we recommend increasing the habitat heterogeneity of native forests to support functionally more diverse Lepidopteran communities.