Fig. 2
Analysis of divergent selection between E. dilemma and E. viridissima. a Boxplot comparing d N and d S values obtained for chemosensory and non-chemosensory (NC) genes (d N and/or d S  ≠ 0). d N was significantly higher for chemosensory than for NC loci while d S had similar values for both sets resulting in elevated mean d N /d S for the chemosensory loci (see text for statistics). *: p < 0.001. b d N /d S plot for 3185 genes reconstructed from the antennal transcriptome analysis. Those genes exhibiting d N /d S >1 have higher non-synonymous to synonymous substitution rates, in agreement with the hypothesis of divergent selection (lower right); those genes with d N /d S <1 exhibit lower non-synonymous to synonymous substitution rates, being consistent with the hypothesis of purifying selection (upper left). Genes with zero d N and d S are not shown and genes with either d N or d S  = 0 are indicated by small points. The set of genes with d N /d S >1 was enriched for chemosensory receptor genes. ORs: Odorant receptors, IRs: Ionotropic receptors, OBPs: Odorant-binding proteins