Figure 1

Relative branch length for the consensus trees of the L1, E1, E7 genes and the URR for the beta and delta papillomaviruses. Evolutionary distances in substitutions per site from present sequences to the last common ancestor of each genera were calculated on the consensus tree estimated after CLUSTALW alignment, distance matrix construction under the neighbor-joining conditions and a Kimura-two parameter nucleotide substitution model, and bootstrapped 10000 times. The two clades were recovered in all the consensus trees, independently of the analysed element. Distances were normalised for each virus individually, with respect to the L1 distance. P values show the results of a two-tailed paired Student's t test for each virus, for the values of the elements connected by the arrow brackets. There is a statistically significant gradient in the divergence distances in the order L1<E1<E7<URR. Divergences in the URR are more than two times higher than in the comparable L1 gene, in both beta and delta clades. The high values of branch-length could account for the low support values obtained for the phylogenetic reconstructions of the URR.