Mitochondrial genomic rearrangements in songbirds

The organization of the mitochondrial genome is generally very conserved am ong vertebrates. Because of this, examination of the rare rearrangements wh ich do occur has been suggested as offering a powerful alternative to phylo genetic analyses of mitochondrial DNA sequences. Here, we report on an avia n mitochondrial rearrangement in a group of oscine passerines (warblers of the genus Phylloscopus). This rearrangement is identical to the mitochondri al organization recently identified in representatives of four orders of bi rds, including subsoscine Passeriformes. The rearrangement involves the mov ement of three genes (tRNA(Pro), NADH6, and rRNA(Glu)) from their normal po sition in birds between tRNA(Thr) and the control region (CR), to a new loc ation between the CR and a novel, supposedly noncoding (NC), region. Our re sults suggest that this derived arrangement cannot be used to distinguish b etween suboscine and oscine passerines, as it has multiple origins both wit hin 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, resp ectively, all of which could be located in the same area of the CR. This su ggests 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 r egions of each species were less pronounced than those between the control or NC regions from the different species, supporting the hypothesis of a si ngle basal rearrangement in the Phylloscopus warblers.