Macrolepidoptera diversity as indicator of microlepidoptera diversity in suburban environments

Abstract Nocturnal lepidoptera (moth) taxa are frequently used as indicators of the quality and conservation value of habitats or as a surrogate of biodiversity. However, most of the existing studies consider only the macrolepidoptera (moths with a wingspan usually >20 mm) or a subset of representative families. Microlepidoptera, which are more difficult to identify to the species level, are rarely taken into account. We examined whether the macrolepidoptera diversity, as well as that of the two most species-rich macrolepidoptera families, could serve as indicator for the microlepidoptera diversity. We conducted full-season quantitative light trapping to collect macro- and microlepidoptera over six years at two suburban localities near Basel (Switzerland) and identified all moths to species level. We recorded a total of 17,404 individuals belonging to 515 species (macrolepidoptera: 290 species (56.3%); microlepidoptera: 225 species (43.7%)). We standardized the samples using the iNEXT methodology. Linear mixed-effects models showed that annual samples of macrolepidoptera and Noctuidae separately were moderately good predictors of microlepidoptera diversity, while this was not the case for Geometridae samples. However, the percentage of microlepidoptera species in weekly catches changed over the season from 45–60% of the total moth species richness in spring and summer to <20% in autumn. Analyses based on weekly samples showed that the prediction of microlepidoptera diversity is weaker than that of annual samples and is highly dependent on the season. Further studies are needed to determine how the lenght and timing of short-term macrolepidoptera samples can be used to predict microlepidoptera diversity.