Whole genome sequence analysis supports the genomic mosaicism of the endangered Hawaiian duck (Anas wyvilliana)

Hybridization and gene flow are now recognized as pervasive evolutionary processes, leading to research foci attempting to understand proximate evolutionary outcomes from such events. Here, we compare the full genomes of a putative recent homoploid hybrid species, the Hawaiian duck, to its parental species, the Hawaiian Islands endemic Laysan duck and the Holarctic mallard. We find that the Hawaiian duck's genome is a mosaic of genetic ancestry of the two parental taxa, with a greater contribution from Laysan duck, but also identify genomic regions harboring Hawaiian duck-derived alleles. Overall, our results support a hybrid origin for the Hawaiian duck and describe potential genomic regions that may have been evolutionarily beneficial for the rise and persistence of this young hybrid species on the main Hawaiian Islands. Finally, our study provides the first reference genomes for the endangered Hawaiian and Laysan ducks, valuable tools for future conservation efforts.