Evolutionary Novelty in a Butterfly Wing Pattern through Enhancer Shuffling.

An important goal in evolutionary biology is to understand the genetic changes underlying novel morphological structures. We investigated the origins of a complex wing pattern found among Amazonian Heliconius butterflies. Genome sequence data from 142 individuals across 17 species identified narrow regions associated with two distinct red colour pattern elements, dennis and ray. We hypothesise that these modules in non-coding sequence represent distinct cis-regulatory loci that control expression of the transcription factor optix, which in turn controls red pattern variation across Heliconius. Phylogenetic analysis of the two elements demonstrated that they have distinct evolutionary histories and that novel adaptive morphological variation was created by shuffling these cis-regulatory modules through recombination between divergent lineages. In addition, recombination of modules into different combinations within species further contributes to diversity. Analysis of the timing of diversification in these two regions supports the hypothesis of introgression moving regulatory modules between species, rather than shared ancestral variation. The dennis phenotype introgressed into Heliconius melpomene at about the same time that ray originated in this group, while ray introgressed back into H. elevatus much more recently. We show that shuffling of existing enhancer elements both within and between species provides a mechanism for rapid diversification and generation of novel morphological combinations during adaptive radiation.This work was funded by BBSRC grant H01439X/1, ERC grant MimEvol and ANR grant HybEvol to MJ.This is the final version of the article. It was first available from PLOS via http://dx.doi.org/10.1371/journal.pbio.100235

The gene cortex controls mimicry and crypsis in butterflies and moths.

The wing patterns of butterflies and moths (Lepidoptera) are diverse and striking examples of evolutionary diversification by natural selection. Lepidopteran wing colour patterns are a key innovation, consisting of arrays of coloured scales. We still lack a general understanding of how these patterns are controlled and whether this control shows any commonality across the 160,000 moth and 17,000 butterfly species. Here, we use fine-scale mapping with population genomics and gene expression analyses to identify a gene, cortex, that regulates pattern switches in multiple species across the mimetic radiation in Heliconius butterflies. cortex belongs to a fast-evolving subfamily of the otherwise highly conserved fizzy family of cell-cycle regulators, suggesting that it probably regulates pigmentation patterning by regulating scale cell development. In parallel with findings in the peppered moth (Biston betularia), our results suggest that this mechanism is common within Lepidoptera and that cortex has become a major target for natural selection acting on colour and pattern variation in this group of insects.We thank the governments of Colombia, Ecuador, Panama and Peru for permission to collect butterflies. This work was funded by a Leverhulme Trust award and BBSRC grant (H01439X/1) to CDJ, NSF grants (DEB 1257689, IOS 1052541) to WOM, an ERC starting grant to MJ and a French National Agency for Research (ANR) grant to VL (ANR-13-JSV7-0003-01). NJN is funded by a NERC fellowship (NE/K008498/1).This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1796

Macroevolutionary shifts of WntA function potentiate butterfly wing-pattern diversity.

Butterfly wing patterns provide a rich comparative framework to study how morphological complexity develops and evolves. Here we used CRISPR/Cas9 somatic mutagenesis to test a patterning role for WntA, a signaling ligand gene previously identified as a hotspot of shape-tuning alleles involved in wing mimicry. We show that WntA loss-of-function causes multiple modifications of pattern elements in seven nymphalid butterfly species. In three butterflies with a conserved wing-pattern arrangement, WntA is necessary for the induction of stripe-like patterns known as symmetry systems and acquired a novel eyespot activator role specific to Vanessa forewings. In two Heliconius species, WntA specifies the boundaries between melanic fields and the light-color patterns that they contour. In the passionvine butterfly Agraulis, WntA removal shows opposite effects on adjacent pattern elements, revealing a dual role across the wing field. Finally, WntA acquired a divergent role in the patterning of interveinous patterns in the monarch, a basal nymphalid butterfly that lacks stripe-like symmetry systems. These results identify WntA as an instructive signal for the prepatterning of a biological system of exuberant diversity and illustrate how shifts in the deployment and effects of a single developmental gene underlie morphological change