Fig. 1

a Cluster expansion of ApoD genes specific to teleost fishes after teleost genome duplication (TGD). Each arrow represents a single gene copy. Genes highlighted in red and orange represent paralogs derived from one common ancestor. Genes colored dark and light green represent paralogs derived from one common ancestor. Phylogeny reconstruction is based on a consensus fish phylogeny [24]. b Maximum likelihood phylogenetic tree reconstruction to infer gene duplication. Bootstrap values > 50% are marked on the branch. Lineage-specific duplication events are labelled. Note that although copy B2b of Gadus morhua is clustered within the B2a clade (labelled with a green star), its bootstrap value is low, which could be due to recent duplication. c The dynamic evolutionary pattern of ApoD genes across the phylogeny of teleost fishes. Highly variable copy numbers are detected in different lineages, especially in the Paracanthopterygii lineage. Stylephorus chordatus has lost all ApoD genes. Compared to copy A1, copy A2 exhibits more variable lineage-specific duplicates in different fishes, with the highest numbers appearing in tilapia (four copies). Copy B1 is absent in the whole clade of Gadiformes. Copy B2 only shows up in the species Danio rerio, Osmerus eperlanus and Parasudis fraserbrunneri. The co-existence of B2a and B2b is common in Percomorphaceae. The largest numbers of lineage-specific duplicated genes are found in tilapia (copy A2), medaka (copy A2) and stickleback (copy B2b) in Percomorphaceae