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Background: Resolving the phylogeny of rapidly radiating lineages presents a challenge when building the Tree of Life. An Old World avian family Prunellidae (Accentors) comprises twelve species that rapidly diversified at the Pliocene-Pleistocene boundary., Results: Here we investigate the phylogenetic relationships of all species of Prunellidae using a chromosome-level de novo assembly of Prunella strophiata and 36 high-coverage resequenced genomes. We use homologous alignments of thousands of exonic and intronic loci to build the coalescent and concatenated phylogenies and recover four different species trees. Topology tests show a large degree of gene tree-species tree discordance but only 40-54% of intronic gene trees and 36-75% of exonic genic trees can be explained by incomplete lineage sorting and gene tree estimation errors. Estimated branch lengths for three successive internal branches in the inferred species trees suggest the existence of an empirical anomaly zone. The most common topology recovered for species in this anomaly zone was not similar to any coalescent or concatenated inference phylogenies, suggesting presence of anomalous gene trees. However, this interpretation is complicated by the presence of gene flow because extensive introgression was detected among these species. When exploring tree topology distributions, introgression, and regional variation in recombination rate, we find that many autosomal regions contain signatures of introgression and thus may mislead phylogenetic inference. Conversely, the phylogenetic signal is concentrated to regions with low-recombination rate, such as the Z chromosome, which are also more resistant to interspecific introgression., Conclusions: Collectively, our results suggest that phylogenomic inference should consider the underlying genomic architecture to maximize the consistency of phylogenomic signal., (© 2024. The Author(s).)

Background: Allopatric speciation has played a particularly important role in archipelagic settings where populations evolve in isolation after colonizing different islands. The Indo-Australasian island realm is an unparalleled natural laboratory of biotic diversification. Here we explore how the level of earth-historic isolation has influenced genetic differentiation across the region by investigating phylogeographic patterns in the Pitta sordida species complex., Results: We generated a de novo genome and compared population genomics of 29 individuals of Pitta sordida from the entire distributional range and we reconstructed phylogenetic relationship using mitogenomes, a multi-nuclear gene dataset and single nucleotide polymorphisms (SNPs). We found deep divergence between an eastern and a western group of taxa across Indo-Australasia. Within both groups we have identified major lineages that are geographically separated into Philippines, Borneo, western Sundaland, and New Guinea, respectively. Although these lineages are genetically well-differentiated, suggesting a long-term isolation, there are signatures of extensive gene flow within each lineage throughout the Pleistocene, despite the wide geographic range occupied by some of them. We found little evidence of hybridization or introgression among the studied taxa, but forsteni from Sulawesi makes an exception. This individual, belonging to the eastern clade, is genetically admixed between the western and eastern clades. Geographically this makes sense as Sulawesi is not far from Borneo that houses a population of hooded pittas that belongs to the western clade., Conclusions: We found that geological vicariance events cannot explain the current genetic differentiation in the Pitta sordida species complex. Instead, the glacial-interglacial cycles may have played a major role therein. During glacials the sea level could be up to 120 m lower than today and land bridges formed within both the Sunda Shelf and the Sahul Shelf permitting dispersal of floral and faunal elements. The geographic distribution of hooded pittas shows the importance of overwater, "stepping-stone" dispersals not only to deep-sea islands, but also from one shelf to the other. The most parsimonious hypothesis is an Asian ancestral home of the Pitta sordida species complex and a colonization from west to east, probably via Wallacea.