Fig. 1.

Phylogenetic relationships among astroviruses based on amino acid replacements (A, B, C) and synonymous codon usage (D, E, F) in ORF1a (A, D), ORF1b (B, E), and ORF2 (C, F). Boxes indicate topological differences between the two phylogenies. The avian astroviruses are in white, the mammalian astroviruses are in gray (human astroviruses—dark gray, non-human astroviruses—light gray). The scale bars represent either the number of amino acid replacements per site or the relative difference in synonymous codon usage between the species. The bootstrap values are shown.