Figure 4

Copy numbers of retroviral endogenous viral elements among birds, American alligator, green turtle, anole lizard, and mammals. Different host groups are colored as red (birds), blue (American alligator, green turtle and anole lizard) and green (mammals). A trend of increasing genome size is also noted. Species are listed from bottom to top in accordance with the bird species order given in Table S6 in Additional file 1, and the order among the American alligator, green turtle, anole lizard, and mammals given in Table S7 in Additional file 1. Asterisks indicate three oscine passerines showing an EVE expansion.