Abstract
BackgroundInformation on larval diet of many holometabolous insects remains incomplete. Carbon (C) and nitrogen (N) stable isotope analysis in adult wing tissue can provide an efficient tool to infer such trophic relationships. The present study examines whether moth feeding guild affiliations taken from literature are reflected in isotopic signatures.ResultsNon-metric multidimensional scaling and permutational analysis of variance indicate that centroids of dietary groups differ significantly. In particular, species whose larvae feed on mosses or aquatic plants deviated from those that consumed vascular land plants. Moth δ15N signatures spanned a broader range, and were less dependent on species identity than δ13C values. Comparison between moth samples and ostensible food sources revealed heterogeneity in the lichenivorous guild, indicating only Lithosia quadra as an obligate lichen feeder. Among root-feeding Agrotis segetum, some specimens appear to have developed on crop plants in forest-adjacent farm land. Reed-feeding stem-borers may partially rely on intermediary trophic levels such as fungal or bacterial growth.ConclusionDiagnostic partitioning of moth dietary guilds based on isotopic signatures alone could not be achieved, but hypotheses on trophic relationships based on often vague literature records could be assessed with high resolution. Hence, the approach is well suited for basic categorization of moths where diet is unknown or notoriously difficult to observe (i.e. Microlepidoptera, lichen-feeders).Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-016-0170-0) contains supplementary material, which is available to authorized users.
Highlights
Information on larval diet of many holometabolous insects remains incomplete
Non-metric multi-dimensional scaling (NMDS) of Euclidean distances based on combined evidence from δ13C and δ15N suggests that dietary guilds among moths can be well distinguished based on stable isotope analysis
There has been little research on this issue, but the results presented here and in other studies [16, 25] suggest that isotopic signatures in adult wing tissue are sufficiently stable to allow inference of larval diet
Summary
Information on larval diet of many holometabolous insects remains incomplete. Carbon (C) and nitrogen (N) stable isotope analysis in adult wing tissue can provide an efficient tool to infer such trophic relationships. The lack of detailed dietary information is partly related to sampling difficulties: Caterpillars are typically cryptic in coloration and behaviour ([9] for comprehensive review), and often occur at low densities Their mere presence on a plant does not necessarily imply a trophic relationship since many species are known to move to neighbouring non-host plants for reasons of predator avoidance [10] or thermoregulation [11]. [13] offer more precise insight, but these approaches are time consuming and only reveal dietary habits during a short time span prior to sampling This may result in misleading or incomplete dietary classification as some species switch diet during their larval development, actively mix diets for nutritional balance [14], or feed opportunistically, exploiting different food sources if and when they are available [15]
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