Mimicry drives convergence in structural and light transmission features of transparent wings in Lepidoptera

Abstract

<jats:title>Abstract</jats:title><jats:p>Müllerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal that advertises their defences to predators. In Lepidoptera, aposematic species typically harbour conspicuous opaque wing colour pattern, which have convergent optical properties, as perceived by predators. Surprisingly, some aposematic mimetic species have partially or totally transparent wings, which raises the question of whether optical properties of such transparent areas are also under selection for convergence. To answer this question and to investigate how transparency is achieved in the first place, we conducted a comparative study of optics and structures of transparent wings in neotropical mimetic clearwing Lepidoptera. We quantified transparency by spectrophotometry and characterised clearwing microstructures and nanostructures by microscopy imaging. We show that transparency is convergent among co-mimics in the eyes of predators, despite a large diversity of underlying micro- and nanostructures. Notably, we reveal that nanostructure density largely influences light transmission. While transparency is primarily produced by modification of microstructure features, nanostructures may provide a way to fine-tune the degree of transparency. This study calls for a change of paradigm in transparent mimetic lepidoptera: transparency not only enables camouflage but can also be part of aposematic signals.</jats:p><jats:sec><jats:title>Significance</jats:title><jats:p>Transparency in animals has long been associated to camouflage, but the existence of aposematic mimetic Lepidoptera with partly transparent wings raises the question of the role of transparency in aposematism. Here, we undertake the first comparative analysis of transparency features in mimetic Lepidoptera. We show that transparency is likely part of the aposematic signal, as light transmission properties are convergent among co-mimics. We also reveal a high diversity of wing structures (scales and wing membrane nanostructures) underlying transparency, which enables fine-tuning the degree of transparency. This study, at the interface between physical optics and evolutionary biology, sheds light on the evolution of transparency in aposematic mimetic lineages and may promote bioinspired applications for transparent materials such as antireflective devices.</jats:p></jats:sec>

Horizontal Transfer of Microbial Toxin Genes to Gall Midge Genomes

“…Higher δ values correspond to higher phylogenetic signals ( Borges et al 2019 ). P -values are calculated as the number of simulations in which the shuffled δ is higher than the realized δ , a strategy utilized in several recent studies ( Pinna et al 2020 ; Ronget et al 2020 ).…”

Developmental, cellular, and biochemical basis of transparency in the glasswing butterflyGreta oto

“…1G-I) (10,23). More recent studies have explored aspects of structural diversity, optical properties, phylogenetic distribution, and ecological relevance of transparency within a wide range of butterflies and moths, highlighting that transparency has evolved multiple times independently and may present evolutionary benefits (13,24,25).…”

“…Lepidoptera are proving to represent an excellent group to investigate transparency on land, but the developmental processes underlying wing transparency are currently unknown. This presents a gap in our understanding of lepidopteran wing evolution and diversification, as transparent butterflies and moths contain multitudes of intriguing scale modifications and sub-wavelength cuticular nanostructures (24,25). We therefore set out to explore the development of wing transparency in the glasswing butterfly Greta oto, which belongs to a diverse tribe (∼393 species) of predominantly transparent neotropical butterflies (26).…”

Partial wing transparency works better when disrupting wing edges: Evidence from a field experiment

“…Transparent elements in these latter species may reduce prey detectability as they are large transparent zones that one would expect to enhance background matching (Arias et al, 2019; McClure et al, 2019). However, transparency in these species could also potentially function as a means of visual communication such as mimicry (Pinna et al, 2021). It is also possible that in the relatively large‐winged Lepidoptera, evolving transparent areas touching wing edges is constrained by factors linked to wing strength or flight dynamics.…”