Day-night gene expression reveals circadian gene as a candidate for diel-niche evolution in moths.

Temporal ecological niche partitioning is an underappreciated driver of speciation. While insects have long been models for circadian biology, the genes and circuits that allow adaptive changes in diel-niches remain poorly understood. We compared gene expression in closely related day- and night-active non-model wild silk moths, with otherwise similar ecologies. Using an ortholog-based pipeline to compare RNA-Seq patterns across two moth species, we find over 25 pairs of gene orthologs showing differential expression. Notably, the gene involved in circadian control, optic lobe and clock neuron development in , shows robust adult circadian mRNA cycling in moth heads. is highly conserved in moths and has additional zinc-finger domains with specific nocturnal and diurnal mutations. We propose as a candidate gene for the diversification of temporal diel-niche in moths.