Maximum likelihood phylogeny of opsin proteins showing clusters of major groupings. Bayesian methods reconstructed a tree with the same topology. Bootstrap support values greater than 50% are denoted. Bayesian posterior probabilities are shown as colored circles at nodes. Red circles indicate 100% support, blue circles indicate >96% support, and black circles indicate >70% support. Gene name abbreviations: 5SR = fifth somatostatin receptor; AR = allatostatin receptor; MAR = muscarinic acetylcholine receptor; MWS = medium-wavelength sensitive; RGR = retinal G protein-coupled receptor; Rh = rhodopsin; SWS = short-wavelength sensitive.