Museomics unravels cryptic diversity in an endemic group of New Guinean songbirds

Deciphering cryptic diversity can have substantial implications for our understanding of evolutionary processes and species conservation. Birds are arguably among the best studied organismal groups, but even in avian clades there are some genera that have not been thoroughly surveyed. This is particularly true for taxa that occur in hyperdiverse biogeographic regions. In this study, we focus on an endemic group of New Guinean birds, the jewel-babblers (genus: Ptilorrhoa), and study the diversification history of all known taxa. We assemble a de novo genome using linked-read sequencing and genomic data for 40 historical specimens. Both phylogenomic and population-genomic analyses strongly support the recovery of a cryptic species and shed new light on the diversification history of this group. The blue jewel-babbler (Ptilorrhoa caerulescens) is a paraphyletic species complex and P. c. nigricrissus is more closely related to the phenotypically distinct and sexually dimorphic P. geislerorum, than to other P. caerulescens subspecies. These findings demonstrate that even in well-studied groups such as birds, cryptic diversity can still be a prevalent reality. Moreover, by deciphering cryptic diversity, we shed new light on the processes driving speciation within Ptilorrhoa and the need to potentially revise the taxonomic status of all subspecies.