Multiple sex chromosomes ofYponomeutaermine moths suggest a role of sexual antagonism in sex chromosome turnover in Lepidoptera

Abstract

AbstractSex chromosome-autosome fusions give rise to neo-sex chromosomes, which provide an insight into early evolution of sex chromosomes and drivers of chromosomal fusions. While sex chromosome-autosome fusions are scarce in vertebrates with female heterogamety (♀ZW/♂ZZ), they are common in moths and butterflies (Lepidoptera), the most species rich group with heterogametic females. This contradicts theoretical model that assumes chromosome fusions to be random and predicts them to be rare in taxa with high chromosome number such as Lepidoptera. In the present study we analyzed sex chromosomes in nine ermine moths of the genusYponomeuta(Yponomeutidae) and their two outgroups,Teinoptila gutella(Yponomeutidae) andPlutella xylostella(Plutellidae). We employed genomicin situhybridization to identify sex chromosomes and used a custom designed microarray to identify Z-linked genes. Our results confirmed a multiple sex chromosome system Z1Z2W to be present inT. gutellaand allYponomeutaspp. except forY. tokyonella. The multiple sex chromosome system resulted from a fusion between the W chromosome and autosome homeologous to theBombyx morichromosome 2 (BmChr2). The BmChr2 bears a cluster of genes with ovary-specific expression which suggests that sexually antagonistic selection could have driven fixation of the fusion in a common ancestor ofYponomeutaandTeinoptilagenera. We hypothesize that sex chromosome turnover in Lepidoptera could be driven by sexual antagonism.