Comparative mitogenomics of the genus Motacilla (Aves, Passeriformes) and its phylogenetic implications

The genus Motacilla belongs to Motacillidae (Passeriformes), where mitochondrial features are poorly understood and phylogeny is controversial. Whole mitochondrial genome (mitogenome) data and large taxon sampling are considered to be ideal strategies to obtain this information. We generated four complete mitogenomes of M.flava, M.cinerea, M.alba and Dendronanthusindicus, and made comparative analyses of Motacilla species combined with mitogenome data from GenBank, and then reconstructed phylogenetic trees based on 37 mitochondrial genes. The mitogenomes of four mitogenome sequences exhibited the same gene order observed in most Passeriformes species. Comparative analyses were performed among all six sampled Motacilla mitogenomes. The complete mitogenomes showed A-skew and C-skew. Most protein-coding genes (PCGs) start with an ATG codon and terminate with a TAA codon. The secondary structures of RNAs were similar among Motacilla and Dendronanthus. All tRNAs except for trnS(agy) could be folded into classic clover-leaf structures. Three domains and several conserved boxes were detected. Phylogenetic analysis of 90 mitogenomes of Passeriformes using maximum likelihood (ML) and Bayesian inference (BI) revealed that Motacilla was a monophyletic group. Among Motacilla species, M.flava and M.tschutschensis showed closer relationships, and M.cinerea was located in a basal position within Motacilla. These data provide important information for better understanding the mitogenomic characteristics and phylogeny of Motacilla.