Positive selection in the B30.2 domain. Distribution of hypervariable and positively selected residues in a multiple alignment of B30.2 domains from representative zebrafish and rainbow trout finTRIMs (Dareftr13: [GenBank: XM_695031], Onmyref21: [GenBank: XM_695031], human TRIM21 (HosaTRIM21) and TRIM5α (HosaTRIM5α). Sites that are less than 80% conserved among zebrafish or among trout sequences are indicated in red. Positively selected sites (among zebrafish finTRIMs: this study; among primate TRIM5α : previous work of Sawyer et al ) are boxed in blue when detected under models 2a and 8. One site was positive under M8 but not under M2 and is boxed in green. β-strands identified from the TRIM21 structure B30.2 sequence are indicated by dark (PRY) or light (SPRY) blue arrows . The variable loop-connecting strands are named VL1–VL6. The four hypervariable regions of the TRIM5α B30.2 domain are underlined . The detailed PAML results for each position under positive selection are available in Additional file 6, Table S4. The purple 'R' indicates the recombination site identified by GARD.