Diversity of sex chromosomes in Sulawesian medaka fishes

Recent genetic and genomic studies have revealed tremendous diversity in sex chromosomes across diverse taxa. Closely related species with different sex chromosomes provide us with excellent opportunities to investigate the driving forces and the consequences of sex chromosome turnover. In the present study, we investigated the diversity of sex chromosomes of 13 Oryzias species from Sulawesi, Indonesia, which diversified during the last 4.86 million years. Using pooled sequencing we found sex chromosomes in 9 species that all had XY systems, with a species being possibly modified by multiple loci. Seven species (O. woworae, O. asinua, O. wolasi, O. matanensis, O. celebensis, O. hadiatyae, and O. dopingdopingensis) share linkage group (LG) 24 as sex chromosomes; however, they differed in the length and magnitude of sequence divergence between the X and Y chromosomes. The sex chromosome of O. eversi was LG4, which has not been reported as a sex chromosome in any other medaka species. In O...