The X chromosome of insects likely predates the origin of Class Insecta

Sex chromosomes have evolved independently multiple times, but why some are conserved for more than 100 million years whereas others turnover rapidly remains an open question. Here, we examine the homology of sex chromosomes across nine orders of insects, plus the outgroup springtails. We find that the X chromosome is likely homologous across insects and springtails; the only exception is in the Lepidoptera, which has lost the X and now has a ZZ/ZW sex chromosome system. These results suggest the ancestral insect X chromosome has persisted for more than 450 million years – the oldest known sex chromosome to date. Further, we propose that the shrinking of gene content of the Dipteran X chromosome has allowed for a burst of sex-chromosome turnover that is absent from other speciose insect orders., This analysis uses publicaly available data. It has been processed through a series of custom scripts (included) and bioinformatics software programs., , Data files and pipeline for:
\"The X chromosome of insects likely predates Class Insecta\"
In Review: Evolution, 2023

#########################################################################################
All data files are publicly available. Table S1 from supplement with this information:
Isoperla grammatica (Plecoptera):
genome: GCA\_945910005.1 (link: https://www.ncbi.nlm.nih.gov/assembly/GCA\_945910005.1/)
RNA: ERR9881692 (link: https://www.ncbi.nlm.nih.gov/sra/?term=ERR9881692)
Schistocerca americana (Orthoptera)
genome: GCF\_021461395.2 (link: https://www.ncbi.nlm.nih.gov/assembly/GCF\_021461395.2/)
Bombyx mori (Lepidoptera)
genome: GCF\_014905235.1 (link: https://www.ncbi.nlm.nih.gov/assembly/GCF\_014905235.1/)
Lucilia cuprina (Diptera)
genome: GCF\_022045245.1 (link: https://www.ncbi.nlm.nih.gov/assembly/GCF\_022045245.1/)
Coccinella septempunctata (Coleoptera)
genome: GCF\_907165205.1 (link: https://www.ncbi.nlm.nih.gov/assembly/GCF\_907165205.1/)
Chrysoperla carnea (Neuropt...