Opsin data from: Multiple axes of visual system diversity in Ithomiini, an ecologically diverse tribe of mimetic butterflies

The striking structural variation seen in arthropod visual systems can be
explained by the overall quantity and spatio-temporal structure of light
within habitats coupled with developmental and physiological constraints.
However, little is currently known about how fine-scale variation in
visual structures arise across shorter evolutionary and ecological scales.
In this study, we characterise patterns of interspecific (between
species), intraspecific (between sexes) and intraindividual (between eye
regions) variation in the visual system of four ithomiine butterfly
species. These species are part of a diverse 26-Myr-old Neotropical
radiation where changes in mimetic colouration are associated with
fine-scale shifts in ecology, such as microhabitat preference. By using a
combination of selection analyses on visual opsin sequences, in-vivo
ophthalmoscopy, micro-computed tomography (micro-CT),
immunohistochemistry, confocal microscopy, and neural tracing, we quantify
and describe physiological, anatomical, and molecular traits involved in
visual processing. Using these data, we provide evidence of substantial
variation within the visual systems of Ithomiini, including: i) relaxed
selection on visual opsins, perhaps mediated by habitat preference, ii)
interspecific shifts in visual system physiology and anatomy, and iii)
extensive sexual dimorphism, including the complete absence of a
butterfly-specific optic neuropil in the males of some species. We
conclude that considerable visual system variation can exist within
diverse insect radiations, hinting at the evolutionary lability of these
systems to rapidly develop specialisations to distinct visual ecologies,
with selection acting at both the perceptual, processing, and molecular
level.