A Release from Developmental Bias Accelerates Morphological Diversification in Butterfly Eyespots
A release from developmental bias accelerates morphological diversification in butterfly eyespots Oskar Brattströma,b,1,2, Kwaku Aduse-Pokua,3, Erik van Bergena,4, Vernon Frenchc, and Paul M. Brakefielda,d aDepartment of Zoology, University of Cambridge, CB2 3EJ Cambridge, United Kingdom; bAfrican Butterfly Research Institute (ABRI), 0800 Nairobi, Kenya; cInstitute of Evolutionary Biology, University of Edinburgh, Edinburgh, EH9 3JT, United Kingdom; and dCambridge University Museum of Zoology, CB2 3EJ Cambridge, United Kingdom Edited by Sean B. Carroll, Howard Hughes Medical Institute, College Park, MD, and approved September 8, 2020 (received for review April 28, 2020) Development can bias the independent evolution of traits sharing cells releasing a signal (e.g., a diffusible morphogen) that spreads ontogenetic pathways, making certain evolutionary changes less out to form a circular concentration gradient (21, 26). The sur- likely. The eyespots commonly found on butterfly wings each have rounding cells have sensitivity thresholds that direct the color of the concentric rings of differing colors, and these serially repeated pigmented scales that are formed. Below a certain signal threshold, pattern elements have been a focus for evo–devo research. In the the cells do not respond and will continue to develop into the butterfly family Nymphalidae, eyespots have been shown to func- normal base color of the wing, effectively forming the outer edge tion in startling or deflecting predators and to be involved in sex- of the eyespot. Despite two decades of research gradually unrav- ual selection. Previous work on a model species of Mycalesina eling the genetic basis of the developmental processes of butterfly butterfly, Bicyclus anynana, has provided insights into the devel- eyespots, the exact nature of the focal signal remains unknown.
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