The gene cortex controls mimicry and crypsis in butterflies and moths

Abstract

The wing patterns of butterflies and moths (Lepidoptera) are diverse and striking examples of evolutionary diversification by natural selection1,2. 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 if there is any commonality across the 160,000 moth and 17,000 butterfly species. Here, we identify a gene, cortex, through fine-scale mapping using population genomics and gene expression analyses, which 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 regulators3, suggesting that it most likely regulates pigmentation patterning through regulation of scale cell development. In parallel with findings in the peppered moth (Biston betularia)4, 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.

Toll ligand Spätzle3 controls melanization in the stripe pattern formation in caterpillars

“…1A), is important to facilitate detection by predators and hasten avoidance learning (3). The molecular mechanism underlying spot formation in adult and larval insects has become more apparent via many studies in Drosophila (4,5), Bombyx mori (6, 7), and several butterflies (8)(9)(10). Although stripe pattern formation is well-studied in vertebrates, such as the zebra (11), rodents (12), and zebrafish (13), the molecular backgrounds of this pattern in insects are largely unknown.…”

Polymorphism at a mimicry supergene maintained by opposing frequency-dependent selection pressures

“…Supergene genotypes were assessed by genotyping the H. numata ortholog of HM00025 (cortex) (GenBank accession no. FP236845.2) included in the supergene P and one of the major genes controlling wing color and pattern variation in Lepidoptera (47). Genotypes were derived from indel and singlenucleotide polymorphisms fully associated with wing color pattern phenotype (47).…”

“…FP236845.2) included in the supergene P and one of the major genes controlling wing color and pattern variation in Lepidoptera (47). Genotypes were derived from indel and singlenucleotide polymorphisms fully associated with wing color pattern phenotype (47). First, total genomic DNA was extracted with the DNeasy Blood and Tissue Kit from Qiagen according to the manufacturer's protocol.…”

Self-Similarity, Distortion Waves, and the Essence of Morphogenesis: A Generalized View of Color Pattern Formation in Butterfly Wings

“…The recent discovery that a cell cycle regulator, cortex, plays a role in the darkening of the wings in butterflies and moths (Nadeau et al 2016;van't Hof et al 2016) may be a surprise for many biologists, but this discovery fits well with the ploidy hypothesis, although it is not discussed in these papers. This cell cycle regulator may control a process of polyploidization of immature scale cells, which determines the final coloration of scales according to the ploidy hypothesis.…”

“…Cellular size increases in the prospective black ring according to the genome size or ploidy level. This process may be regulated by the cortex gene, which has been identified recently (Nadeau et al 2016;van't Hof et al 2016). The final cellular size or the degrees of polyploidy then determine a repertoire of pigment synthesis genes to be expressed.…”