Fig. 1

Phylogeny of Lepidoptera IRs. The maximum-likelihood phylogenetic tree is based on a protein sequence alignment of ionotropic receptors (IRs) from A. segetum, B. mori [29], P. xylostella [36], H. armigera [36], D. melanogaster [6, 29], and A. gambiae [29, 45]. The tree was rooted with the lineage of IR8a and IR25a receptors. The IRs from different species are color coded as indicated in the figure. The monophyletic IR groups are noted on the tree, with the light blue color indicating “Lepidoptera-specific IR groups.” The large IR7d, IR75p, and IR75q expansions are indicated by red branches, and the entire putative “expanded acid-sensing cluster” (IR75d however responding to an amine in Drosophila) is highlighted in yellow. The five IR75p and IR75q receptors functionally assayed in this study are marked with asterisks. Bootstrap support (100 replicates) values over 0.7 are shown at corresponding nodes