Molecular systematics and plumage coloration evolution of an enigmatic babbler (Pomatorhinus ruficollis) in East Asia

•We infer the phylogeny of the Pomatorhinus ruficollis species complex.•We examine two mitochondrial genes and five nuclear regions.•A group of P. schisticeps is lumped into P. ruficollis.•The Taiwanese subspecies merits a specific status (named as P. musicus).•Breast-streaking coloration in P. ruficollis and P. musicus is evolutionarily labile, and could mislead taxon diagnosis.

The streak-breasted scimitar babbler, Pomatorhinus ruficollis, is a polytypic and taxonomically enigmatic babbler common in southern, eastern, and southeastern Asia. To infer the phylogeny of the P. ruficollis, we examined the sequences of two complete mitochondrial genes (2184 bp in total) from fourteen of the fifteen known subspecies, and an additional five nuclear genes (2657 bp in total) from ten subspecies. The mitochondrial phylogeny indicates four major clades with large geographical identity in P. ruficollis and paraphyly of the P. ruficollis species complex, with the inclusion of the olivaceus group of congeneric P. schisticeps. Together with their interbreeding in northern Indochina, we propose to lump this group into P. ruficollis. Analysis of both multilocus networks and species-tree inference recovered poor phylogenetic structure among mainland/ Hainan subspecies and exclusive groupings of the Taiwanese subspecies, consistent with the recent taxonomic revision of its species status. Our analyses also suggest strong incongruence between the morphological-based classification and molecular systematics, implying the strength of multilocus data for taxonomy.

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