Maximum likelihood tree inferred from the amino acid alignment of dcr-1 sequences. The same topology was found with Bayesian inference and maximum parsimony except for the lack of monophyly of the Aphidini in the latter method. Bootstrap values are shown only when higher that 50%. a1: allele 1; a2: allele 2. For each copy of the gene, the value of the ratio of non-synonymous to synonymous rates (ω) resulting from the “two-ratio” model is shown (see Results), reflecting the difference in evolutionary pressures acting on the different copies, though less marked than for ago-1.