Fig. 1: Phylogenetic relationships and syntenic architecture of cyclostomes and gnathostomes.
a, The brown hagfish, Eptatretus atami (photo credit, M. Suzuki). b, Summary of deuterostome phylogeny based on 176 selected genes (61,939 positions) using a site-heterogeneous model (CAT+GTR). This topology is robust to compositional heterogeneity and similar to what was obtained with 1,467 genes using a site-homogeneous partitioned model (see Methods, Supplementary Note 1 and Extended Data Fig. 2). c, Karyograms showing the ancestry of hagfish, lamprey and gar chromosomes in terms of chordate linkage groups (CLGs A1, A2 and B–Q) described previously19,35 (see also ref. 20 and Supplementary Note 2). Coloured bins contain 20 genes and only genes from CLGs with significant enrichment (Fisher’s exact test) are counted (Methods). Hagfish, lamprey and gar silhouettes downloaded from PhyloPic (credit to Gareth Monger for lamprey). d, Conserved syntenies show that hagfish chromosomes are typically fusions of multiple lamprey chromosomes. Lines connect orthologous genes and are coloured according to the ancestral chordate linkage groups (colour legend in c).
