Molecular and phylogenetic analyses reveal mammalian-like clockwork in the honey bee (Apis mellifera) and shed new light on the molecular evolution of the circadian clock

Brain transcript abundance over time in foragers entrained and collected in LD illumination regime. The plots show the correlation between average (±SE) relative mRNA levels for each time point (filled circles and bars) and a cosinus model with a cycle of 23–25 h (continuous line) for bees from colony S1. (A) amPeriod; (B) amClock; (C) amCrypto-chrome; (D) AmCycle; (E) AmTimeout. In parentheses are the adjusted R² and period of the cosinus model for each gene. Time points with different letters are significantly different (ANOVA, P < 0.05; LSD post hoc test, P < 0.05). In two additional experiments, each with bees from a different, independent colony, we obtained similar results (see text for details). The bars at the bottom of plots indicate the illumination regime during sample collection. Black bar indicates dark; open bar, light. Sample size = 6.