Associating the structure of Lepidoptera-plant interaction networks across clades and life stages to environmental gradients

Aim: The spatial-structural patterns of plant-insect interaction networks, particularly their associations with landscape-scale environmental factors, remain poorly understood. We apply data-driven network constructions that integrate biogeographic and trophic interaction knowledge to uncover how Lepidoptera- plant networks vary across environmental gradients in a real-world landscape.

Location: The 36,000 km^2 German state Baden-Württemberg, Central Europe.

Taxon: Lepidoptera insects and angiosperm plants.

Materials and Methods: We integrated extensive data of Lepidoptera- plant occurrences and interactions to infer local interaction networks across Baden-Württemberg, encompassing 3148 plant and 980 Lepidoptera species, covering butterflies, Noctuoid moths, Geometrid moths, and Bombycoid moths. We quantified clade- and life-stage-specific network structures and related them to GIS-informed environmental conditions, thereby revealing the spatial (environmental) patterns and potential drivers of network variations.

Results: Spanning shared environmental gradients, Lepidoptera clades and life stages formed various interaction structures with plants and exhibit distinct spatial-structural patterns. For all Lepidoptera groups, except Geometrid moths, potential diet across life stages broadened toward low-elevation farmlands. The larval and adult networks of butterflies became less modular with farmland coverage; the same for adult Noctuoid moths, but the inverse for adult Geometrid moths. With increasing elevation, the larval and adult networks of Noctuoid moths became less and more modular, respectively, whereas Geometrid adult networks became more modular. While the adult dietary niche of butterflies overlapped more at low elevation, those of Noctuoid and Geometrid moths further associated with land cover and overlapped more toward low- and high-elevation farmlands, respectively.

Main Conclusions: The spatial-structural patterns of Lepidoptera-plant networks vary

along geo-climate and land-cover gradients in ways depending on the Lepidoptera's clade and life stage. The driving mechanisms likely include both evolutionary (e.g., resource-consumer [co-]evolution) and ecological (e.g., competitive exclusion) processes, and differentially affect Lepidoptera across clades and life stages. These findings pinpoint conservation implications at both species and community levels, with potential trade-offs for managing different Lepidoptera-plant communities under environmental changes.

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Figure 2. The first two principal components of environmental factors (PC1 and PC2, considered as axes of gradients), and the richness of plants and the four Lepidoptera clades across these two axes as 3D scatterplots. The planes in the 3D scatterplots are regression planes of the observed values, whose colour fade toward the low-value end.

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Published in Journal of Biogeography, 2024

Volume (Early View)

Authors: Hsi-Cheng Ho, Florian Altermatt

Full text: https://onlinelibrary.wiley.com/doi/10.1111/jbi.14776