Field evidence for colour mimicry overshadowing morphological mimicry

Abstract

Imperfect mimicry may be maintained when the various components of an aposematic signal have different salience for predators. Experimental laboratory studies provide robust evidence for this phenomenon. Yet, evidence from natural settings remains scarce. We studied how natural bird predators assess multiple features in a multicomponent aposematic signal in the Neotropical ‘clear wing complex’ mimicry ring, dominated by glasswing butterflies. We evaluated two components of the aposematic signal, wing colouration and wing morphology, in a predation experiment based on artificial replicas of glasswing butterflies (model) and Polythoridae damselflies (mimics) in their natural habitat. We also studied the extent of the colour aposematic signal in the local insect community. Finally, we inspected the nanostructures responsible for this convergent colour signal, expected to highly differ between these phylogenetically distinct species. Our results provide direct evidence for a stronger salience of wing colouration than wing morphology, as well as stronger selection on imperfect than in perfect colour mimics. Additionally, investigations of how birds perceive wing colouration of the local insect community provides further evidence that a UV‐reflective white colouration is being selected as the colour aposematic signal of the mimicry ring. Using electron microscopy, we also suggest that damselflies have convergently evolved the warning colouration through a pre‐adaptation. These findings provide a solid complement to previous experimental evidence suggesting a key influence of the cognitive assessment of predators driving the evolution of aposematic signals and mimicry rings.

Multimodal Aposematic Defenses Through the Predation Sequence

“…Ultraviolet (UV) components of the color pattern differ between these two genotypes especially in the forewings (Nokelainen in prep a), and therefore it is possible that birds are responding to UV-reflectance by delaying their attack of prey. Indeed, UV reflective white color is used as a warning signal in other lepidopteran species (Corral-Lopez et al, 2020), although in some earlier experiments UV-reflectance was found to invite rather than deter attacks by birds (Lyytinen et al, 2001(Lyytinen et al, , 2004.…”

Convergent flight morphology among Müllerian mimic mutualists

“…1996), and is perhaps strong enough, in combination with their numerical dominance in mimicry complexes (Poole 1970; Beccaloni 1997a), that close morphological resemblance among color pattern models is not needed for an effective signal (i.e., color similarity is sufficient even with a poor match in morphology [Corral‐Lopez et al. 2021]). Similarity in size, however, which was repeatedly shown to be important in analyses here, may be an important morphological variable in shaping diversity in mimetic communities (Joron and Mallet 1998).…”

Birds learn to avoid aposematic prey by using the appearance of host plants

“…It is widely accepted that the color of aposematic prey warning signals is, in comparison to their body shape or pattern elements, most important to birds that are learning to avoid them. 9,10,17,18 Given this, we designed our second experiment to assess whether the conspicuous yellow flowers of ragwort provided the cue for avoidance, as birds could equally well have learned to avoid the plant's overall shape or locations where cinnabars had been encountered. The experiment was run immediately after phase 3 of Experiment 1 (educated predators) but in different locations.…”