Gustatory receptor (GR) gene family phylogeny including newly annotated genes of three honey bee species. The maximum likelihood tree contained two clades, one including a single ortholog of all putatively functional GRs previously described in A. mellifera (in orange) in each species (blue: A. dorsata; gray: A. florea), and the XYZ clade (supported with 99% bootstrap support) previously thought to be entirely pseudogenized (Robertson and Wanner 2006; Sadd et al. 2015). Five newly identified full-length GRs for A. mellifera are highlighted in pink, some of which are among the newly identified XYZ GRs (four in A. mellifera, 15 in A. florea, and 19 in A. dorsata). All GR groupings outside the XYZ clade have high bootstrap support (for exact support values, see Supplemental Fig. S2), highlighting the conservation of GR gene number in this group across Apis. In addition to >50 small fragments with homology to GRs (light green, only A. mellifera fragments shown), we newly identified a number of full-length genes in the XYZ clade, all of which are supported by gene expression data in A. mellifera. The fragments are included here to represent all of our results, although the GR phylogeny is much clearer without them (Supplemental Fig. S2). With 16–26 putatively functional GRs per species, honey bees are similar to other corbiculate bees (Brand and Ramírez 2017), suggesting that the sense of taste in honey bees is more sophisticated than previously thought.
