Fig. 4

Tandem duplication and expansion of genes related to innate immune recognition has occurred in all three bivalve lineages. a Genes that contain selected Pfam domain candidates related to recognition of non-self antigens. See also Additional file 1: Table S7. b Unrooted maximum likelihood molecular phylogeny of C1q domain sequences of three mollusc genomes (Pinctada fucata: purple, Crassostrea gigas: green, and Lottia gigantea: black), and MgC1q proteins of Mytilus galloprovincialis (red). Wedges indicate the merged gene group, which is composed of sequences only from bivalve species, and the number of constituent genes shown in the arc. Wedges without numbers indicate groups that include two genes. Merged groups that contain two or more tandemly arranged genes in the genome are marked with asterisks. Branches showing orthologous gene groups of three bivalves are highlighted in yellow. Nodes supported with high bootstrap values (≥80 %) are marked with black dots. Branches with slashes were collapsed in order to fit the tree onto the page. The scale bar represents expected substitutions per site in the aligned regions. C1q domain sequences with lengths of 100 amino acids or more were used for analysis with the WAG + GAMMA + F model