Fig. 3

Phylogenetic tree of the Stomoxys calcitrans GRs with those of Drosophila melanogaster and Musca domestica. Maximum likelihood tree rooted by divergent carbon dioxide and sugar receptor subfamilies as the outgroup. The S. calcitrans and M. domestica lineages are highlighted in teal and blue, respectively, while D. melanogaster lineages are in mustard. Support levels from the approximate likelihood-ratio test (aLRT) from the PhyML v3.0 web server are shown. Subfamilies and individual or clustered Drosophila genes are indicated outside the circle to facilitate finding them in the tree. Four clades of candidate bitter receptors that are expanded in the muscids are highlighted. Scale bar indicates amino acid substitutions per site. The full phylogenetic tree can be found in Additional file 1: Figure S11