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Wing scale ultrastructure underlying convergent and divergent iridescent colours in mimetic Heliconius butterflies

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posted on 09.05.2018, 10:11 by Andrew J. Parnell, James E. Bradford, Emma V. Curran, Adam L. Washington, Gracie Adams, Melanie N. Brien, Stephanie L. Burg, Carlos Morochz, Patrick A. Fairclough, Pete Vukusic, Simon Martin, Scott Doak, Nicola J. Nadeau
Iridescence is an optical phenomenon whereby colour changes with the illumination and viewing angle. It can be produced by thin film interference or diffraction. Iridescent optical structures are fairly common in nature, but relatively little is known about their production or evolution. Here we describe the structures responsible for producing blue-green iridescent colour in Heliconius butterflies. Overall the wing scale structures of iridescent and non-iridescent Heliconius species are very similar, both having longitudinal ridges joined by cross-ribs. However, iridescent scales have ridges composed of layered lamellae, which act as multilayer reflectors. Differences in brightness between species can be explained by the extent of overlap of the lamellae and their curvature as well as the density of ridges on the scale. Heliconius are well known for their Mullerian mimicry. We find that iridescent structural colour is not closely matched between co-mimetic species. Differences appear less pronounced in models of Heliconius vision than models of avian vision, suggesting that they are not driven by selection to avoid heterospecific courtship by co-mimics. Ridge profiles appear to evolve relatively slowly, being similar between closely related taxa, while ridge density evolves faster and is similar between distantly related co-mimics.

Funding

This work was funded by a Natural Environment Research Council (NERC) fellowship (NE/K008498/1) to N.J.N. J.E.B. was funded under the NERC Research Experience Placements (REP) scheme. E.C. and M.B. are funded by the NERC doctoral training partnership, ACCE. A.L.W. was funded via InnovateUK.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Journal of the Royal Society Interface

Volume

15

Issue

141

Citation

PARNELL, A.J. ... et al, 2018. Wing scale ultrastructure underlying convergent and divergent iridescent colours in mimetic Heliconius butterflies. Journal of the Royal Society Interface, 15 (141), 20170948.

Publisher

Royal Society, The © The Authors

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/

Acceptance date

26/03/2018

Publication date

2018

Notes

This is an Open Access Article. It is published by Royal Society, The under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

eISSN

1742-5662

Language

en

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