show Abstracthide AbstractThis study assesses the differentiation of sex chromosomes in 3 populations of Rana temporaria in Fennoscandia. We use RNA-sequencing from the gonads of 5 males and 5 females from two populations (Ammarnas and Tvedora) and 5 males and 4 females in one population (Kilpisjarvi) to characterize the sex chromosomes. We find that each population has a unique sex chromosome complement.