Fig. 4

Strong negative and rare positive selection in ora genes from ray-finned fish. Predicted selective pressure for single codons is shown as consensus dN/dS values for fixed effects likelihood (FEL) algorithm and single likelihood ancestor counting (SLAC). a Numbers of negatively (blue) and positively (red) selected codons of each ora gene depicted as bar chart. 117, 106, 123, 110 and 51 negatively selected codons were identified in ora1, ora2, ora3, ora4, ora5 and ora6, respectively. One positively selected codon was predicted for ora3 and ora6. b Positions of sites with positive and negative selective pressure within the coding sequences are illustrated as snake plots for ORA1, ORA3 and ORA6. The schematic representations of these receptors were drawn based on the respective degapped codon-based nucleotide alignments, which were generated from the corresponding amino acid alignments