RT Journal Article
SR Electronic
T1 A phylogenomic framework and timescale for comparative genomics and evolutionary developmental biology of tunicates
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 236448
DO 10.1101/236448
A1 Frédéric Delsuc
A1 Hervé Philippe
A1 Georgia Tsagkogeorga
A1 Paul Simion
A1 Marie-Ka Tilak
A1 Xavier Turon
A1 Susanna López-Legentil
A1 Jacques Piette
A1 Patrick Lemaire
A1 Emmanuel J. P. Douzery
YR 2017
UL http://biorxiv.org/content/early/2017/12/19/236448.abstract
AB Background Tunicates are the closest relatives of vertebrates and are widely used as models to study the evolutionary developmental biology of chordates. Their phylogeny, however, remains poorly understood and to date, only the 18S rRNA nuclear gene and mitogenomes have been used to delineate the major groups of tunicates. To further resolve their evolutionary relationships and provide a first estimate of their divergence times, we used a transcriptomic approach to build a supermatrix consisting of 258 evolutionarily conserved orthologous genes from representative species of all major tunicate lineages.Results Phylogenetic analyses using site-heterogeneous CAT mixture models of amino acid sequence evolution resulted in a strongly supported tree topology resolving the relationships among four major tunicate clades: 1) Appendicularia, 2) Thaliacea + Phlebobranchia + Aplousobranchia, 3) Molgulidae, and 4) Styelidae + Pyuridae. Notably, the morphologically derived Thaliacea are confirmed as the sister-group of the clade uniting Phlebobranchia + Aplousobranchia within which the precise position of the model ascidian genus Ciona remains uncertain. Relaxed molecular clock analyses accommodating the accelerated evolutionary rate of tunicates reveal ancient diversification (∼450-350 million years ago) among the major groups and allow comparing their evolutionary age with respect to the major vertebrate model lineages.Conclusions Our study represents the most comprehensive phylogenomic dataset so far available for tunicates. It offers a reference phylogenetic framework and first tentative timescale for tunicates, allowing a direct comparison with vertebrate model species in future comparative genomics and evolutionary developmental biology studies.