Color polymorphism is one of the most diverse phenotypes in nature that plays widespread roles in local adaptation, speciation, and hybridization. In Lepidoptera, despite great efforts in addressing mimicry and introgression in butterflies, characterizing the mutational events underlying color variation and associated evolutionary history are still lacking in moths. Here, we focus on geometrid moths which exhibited black and grey body color polymorphism in natural populations. Based on bulked pooling-resequencing of backcross progeny, we characterize a candidate 700-kb locus on chromosome that underlies the color variation. Interestingly, this region is homologous to the targets for controlling wing pattern polymorphisms and mimicry in many butterflies, but pinpoints to a different gene that encodes poly(a)-specific ribonuclease. Functional studies in geometrids and the lepidopteran model, Bombyx mori, support the role of target genes in causing melanism in moths. We further sample and analyze genome-wide variations in additional wild-caught populations and find a divergent sub-pattern within this candidate region, along with strong signal of selection. Based on the wild distribution pattern, we last discuss the potential ecological fitness of this color variation in geometrid moths. Taken together, our study shows the parallel evolved color variation in lepidopterans is controlled by a convergent hotspot region.
Parallel evolution of a convergent locus underlying lepidopteran melanism