OBP gene repertoire in the 12 Drosophila spp. Values on the right part indicate the number of putative functional genes and pseudogenes (in parenthesis). Values in red indicate the inferred number of genes at the ancestral nodes of the phylogenetic tree. Values above the branches show the number of gene gains (gene duplications events), and below the branches X(Y) represent the total number of losses (deletions plus pseudogenization events [X]) and pseudogenization events (Y). OBP, odorant-binding protein.