Phylogenies of chloroviruses and algal hosts. A: ML tree of chloroviruses based on a concatenated alignment of 32 core protein families (7762 gap-free sites). The phylogenetic tree was computed using the WAG + G + I substitution model. Branch support was estimated from 1000 bootstrap replicates. We only show bootstrap values < 90%. Ostreococcus viruses serve as an outgroup to root the tree. B: ML tree of algal hosts based on 18S RNA alignment (2266 gap-free sites). The phylogenetic tree was computed using the GTR + G + I substitution model. All interior branches received maximal support (100%). Parachlorella spp. are used as outgroup.