Mitochondrial genomic rearrangements in songbirds

The organization of the mitochondrial genome is generally very conserved among vertebrates. Because of this, examination of the rare rearrangements which do occur has been suggested as offering a powerful alternative to phylogenetic analyses of mitochondrial DNA sequences. Here, we report on an avian mitochondrial rearrangement in a group of oscine passerines (warblers of the genus Phylloscopus). This rearrangement is identical to the mitochondrial organization recently identified in representatives of four orders of birds, including subsoscine Passeriformes. The rearrangement involves the movement of three genes (tRNA(Pro), NADH6, and tRNA(Glu)) from their normal position in birds between tRNA(Thr) and the control region (CR), to a new location between the CR and a novel, supposedly noncoding (NC), region. Our results suggest that this derived arrangement cannot be used to distinguish between suboscine and oscine passerines, as it has multiple origins both within Passeriformes and within birds as a whole. We found short stretches of DNA with high degrees of similarity between the CR and each NC region, respectively, all of which could be located in the same area of the CR. This suggests that the CR and the NC region are homologous and that the mechanism behind this mitochondrial rearrangement is a tandem duplication followed by multiple deletions. However, the similarities between the control and NC regions of each species were less pronounced than those between the control or NC regions from the different species, supporting the hypothesis of a single basal rearrangement in the Phylloscopus warblers.