In this editorial letter, we summarize the current challenges in the field of sex chromosome evolution and introduce the 17 manuscripts which together provide insights into the diversity of sex chromosome evolutionary rates and mechanisms. Across the tree of life, many species with separate sexes have evolved sex chromosomes, on which (master) sex-determining genes are located to determine the sex of an individual (Bachtrog et al., 2014; Beukeboom & Perrin, 2014).
Sex-linked inheritance makes sex chromosomes a hotspot for sex-specific and sexual selection, and independently evolved sex chromosomes show convergent evolutionary and genomic characteristics (Ellison & Bachtrog, 2019; Furman et al., 2020; Hughes & Rozen, 2012; Ming et al., 2011).