Gene expression
Eastern and western monarchs were randomly selected, flown on the flight mill for two minutes, and immediately frozen in liquid nitrogen prior to RNA extraction. Overall, the expression of the six candidate genes varied widely between individual butterflies, and expression of several genes tended to be higher in western monarchs (Fig. 8). Mann-Whitney U tests showed that western monarchs had significantly higher expression of the myosin heavy chain gene associated with non-muscular motor activity (Fig. 8; DPOGS215054; P=0.039).