Phylogenetic analysis of the winter geometrid genus Inurois reveals repeated reproductive season shifts

- In genus Inurois, species reproduce either in early or late winter species.
- We examined evolution of reproductive season by phylogenetic analyses.
- Phylogenetic analysis revealed repeated reproductive season shifts in the genus.
- Four of 13 speciation events are associated with reproductive season shift.

Winter geometrid moths belonging to the genus Inurois comprise nine species that reproduce during early winter, three species that reproduce in late winter, and polymorphic species with genetically diverged early and late winter populations that co-occur widely across the species' range. In our previous studies, we demonstrated that differences in reproductive timing resulted in allochronic reproductive isolation between sympatric populations. In the present study, to assess the evolutionary pattern of reproductive timing within the genus, we determined the phylogenetic relationships among species using nuclear and mitochondrial gene sequences. Nuclear gene tree showed that reproductive season shifts occurred independently in four of 13 divergence events. In two divergence events, allochronic sister lineages were formed in sympatry, suggesting that the segregation of the reproductive season was associated with diversification in the genus Inurois. We also found that the mitochondrial gene tree was quite different from the nuclear gene tree and that mitochondrial introgression may have occurred in a few cases. Although it remains unclear whether early and late winter species actually have hybridized with each other and how strong or stable is the reproductive isolation provided by the reproductive season segregation, our study illuminates the potential importance of allochronic isolation in the diversification process of the genus Inurois.

58