Figure 1: Characterization of ASHCEs.

(a) Average sizes of gene families in different vertebrate species. Species in different phylogenetic groups were coloured in different colours. See Supplementary Table 1 for the list of species used in this analysis. (b) Illustration of two types of ASHCEs. The type I ASHCEs are conserved in birds but have no homologous sequence in other vertebrate outgroups; the type II ASHCEs are conserved in birds and have rudimentary homologous sequences in outgroup species, but the sequence conservation is significantly low to be detected as homologous between birds and other vertebrates. See Methods section for more details about the identification method of ASHCEs. (c) Functional classification of all HCEs and ASHCEs in chicken genome.