The impact of mitochondrial genome analyses on the understanding of deuterostome phylogeny

Deuterostomia, one of the three major lineages of Bilateria, comprises many well-known animals such as vertebrates, sea squirts, sea stars and sea urchins. Whereas monophyly of Deuterostomia and several subtaxa is well supported, the relationships of these to each other and, hence, deuterostome relationships are still uncertain. To address these issues in deuterostome phylogeny we analyzed datasets comprising more than 300 complete deuterostome mitochondrial genomes. Based on sequence information, the results revealed support for several relationships such as a basal position of Xenoturbella within Deuterostomia or for taxa like Craniota or Ambulacraria, but yielded also problems in some taxa, e.g. Tunicata, Pterobranchia and Ophiuroidea, due to long-branch artifacts. However, within tunicates the relationships are well supported. Variation in the genetic code was also informative and, e.g., supported the taxon Ambulacraria including Pterobranchia.

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► Comprehensive analyses of more than 300 complete mitochondrial genomes were done.
► Monophyly of each major deuterostome lineage and some subgroups was supported.
► Our data clearly supported monophyly of Ambulacraria (Hemichordata + Echinodermata).
► Xenoturbella is sister to all other deuterostomes.
► The placement of Pterobranchia, Tunicata and Ophiuroidea is still problematic.