Lichenostomus cassidix Chromosome-length assembly. Lichenostomus cassidix isolate:B80296

The helmeted honeyeater, Lichenostomus melanops cassidix, is an endangered subspecies of the common southeastern Australian yellow-tufted honeyeater (L. melanops), named for its helmet of head feathers. Only about 230 cassidix individuals remain in the wild despite decades of supplementation by an intensive captive breeding program. The single remaining cassidix population lost much of its genetic diversity over the last decades and now experiences strong inbreeding depression, with the most inbred birds producing only one-tenth as many young as the least inbred birds. To reverse population declines caused by inbreeding depression, genetic rescue was recommended and trialled in captivity, where cassidix were paired with birds from a closely related subspecies, L. m. gippslandicus diverged from the common ancestor up to 50,000 years ago. The hybrid young produced from such pairings are being released into the wild since 2019. To understand how inbreeding eroded functional genetic diversity in cassidix and how admixture between cassidix and gippslandicus can influence cassidix phenotypes, a reference genome for L. melanops is required. Here, we sequence and assemble a genome of a helmeted honeyeater (subspecies cassidix). This chromosome-length genome builds on the previous reference genome, and serves as the basis for genomic research in L. melanops and related taxa important for understanding evolution, and informing conservation management of threatened species.