Fig. 4

Distribution of positively selected sites on the ant odorant receptor proteins. a Each protein schematic represents an odorant receptor from gene clades that show signatures of positive selection (Tables 1, 2). Protein topology was predicted using TOPCON, TMHMM and TOPPRED. These proteins have 7 transmembrane domains with an intracellular N terminus and extracellular C terminus (TM transmembrane membrane region, IN intracellular loop, OUT extra cellular loop). Each circle indicates an amino acid. Positively selected sites (PSSs) predicted under model M2a are highlighted as follow: grey circle PSSs with posterior probability (PPs) > 50 %, black circle PSSs with PPs > 95 %, black square PSSs with PPs > 99 %. b Proportion of positively selected sites in each protein region. c Proportion of PSSs in each TM region (left) and proportion of PSSs in each intracellular loop (right)