Phylogenetic tree with the proportion of solo-LTRs (the inner circle) and the ratio of solo-LTR (outer circle) in birds ( n =362), reptiles ( n =23), and mammals ( n =20). The inner circle represents the proportion of solo-LTRs relative to the genome size. The outer circle represents the ratio of solo-LTRs to total LTRs length, indicating the frequency of solo-LTRs formation. Taxonomic information follows classifications in Howard and Moore 83 .
