Species-level paraphyly inferred from mitochondrial gene trees is a prevalent phenomenon in taxonomy and systematics, but there are several potential causes that are not easily explained by currently used methods. The present study aims to test the underlying causes behind the observed paraphyly of Streak-breasted Scimitar Babbler (Pomatorhinus ruficollis) via statistical analyses of four mitochondrial (mtDNA) and nine nuclear (nuDNA) genes. Mitochondrial gene trees show paraphyly of P. ruficollis with respect to the Taiwan Scimitar Babbler (P. musicus), but nuclear genealogies support a sister-group relationship. Predictive coalescent simulations imply several hypothetical explanations, the most likely being mitochondrial capture of P. ruficollis by P. musicus for the observed cyto-nuclear incongruence. Further Approximate Bayesian Computation suggests a unidirectional introgression model with substantial level of gene flow from P. ruficollis to P. musicus during their initial divergence during the Late Pleistocene. This specific observation frames several potential causes for incongruent outcomes of mitochondrial and nuclear introgression in general, and on the whole, our results underscore the strength of multiple independent loci for species delimitation and importance of testing hypotheses that explain disparate causes of mitochondrial gene-tree paraphyly.

1.raw sequence dataset of nulcear loci2.complete genetypic dataset of nuclear loci_for ABC analysis3.partial genetypic dataset of nuclear loci_for multilocus network analysis4. partial genetypic dataset of nuclear loci for species tree analysis5.dataset for evolutionary rate estimation6. mitochondrial raw sequences and haplotypic dataset