We report the discovery of a novel neo-sex chromosome in an African warbler, Sylvietta brachyura (northern crombec; Macrosphenidae). This species is part of the Sylvioidea superfamily, where four separate autosome–sex chromosome translocation events have previously been discovered via comparative genomics of 11 of the 22 families in this clade. Our discovery here resulted from analyses of genomic data of single-species representatives from three additional Sylvioidea families (Macrosphenidae, Pycnonotidae, and Leiothrichidae). In all three species, we confirmed the translocation of a part of chromosome 4A to the sex chromosomes, which originated basally in Sylvioidea. In S. brachyura, we found that a part of chromosome 8 has been translocated to the sex chromosomes, forming a unique neo-sex chromosome in this lineage. Furthermore, the non-recombining part of 4A in S. brachyura is smaller than in other Sylvioidea species which suggests that recombination continued along this region after the fusion event in the Sylvioidea ancestor. These findings reveal additional sex chromosome diversity among the Sylvioidea, where five separate translocation events are now confirmed.

Dataset content:

1. config_files.zip: Configuration files that were used to run the pipeline findZX (Sigeman et al. 2022; https://doi.org/10.1186/s12864-022-08432-9) on our three study species (Argya altirostris, Pycnonotus barbatus, and Sylvietta brachyura). Instructions on how to install and run findZX are on the GitHub page (https://github.com/hsigeman/findZX). Command-line instructions for how to replicate the results in this paper are in the Supplementary Information.

2. findZX_results.zip: Output tables and plots from the findZX analyses of Argya altirostris, Pycnonotus barbatus, and Sylvietta brachyura.