Phylogenetic tree of 26 iridoviral core protein sequences from 20 completely sequenced iridoviruses. Consensus bootstrap confidence values are indicated at the nodes of the branches. The host of each virus and viral genus are listed at the right. Two subgroups, such as “Amphibian subgroup” and “Fish subgroup”, were revealed in genus Ranavirus. ADRV appears in the amphibian subgroup, and it is most closely related to CMTV, RGV, FV3 and TFV. The sequences used for this analysis are collected in Additional file 1.