Physiological correlates of genetic variation for rate of behavioral development in the honeybee, Apis mellifera

Two factors that influence age at onset of foraging in honeybees are juveni le hormone (JH) and colony age demography (older bees inhibit behavioral de velopment of younger bees). We tested the hypothesis that genetic variation among bees for these factors influences genetic variation in behavioral de velopment. Pairs of colonies showing genetic differences in rates of behavi oral development were identified in a screening experiment and bees from th ese colonies were used for physiological and behavioral assays. Six pairs w ere assayed, three with European bees only and three with both European and Africanized bees. There was genetic variation for the following four compo nents: (1) production of JH in four pairs (experiment 1); (2) sensitivity t o JH in three pairs (experiment 2); (3) sensitivity to social inhibition in three pairs (experiment 3), and (4) potency of social inhibition in four p airs (experiment 4). Cross-fostering assays (experiment 5), which allowed a ll four components to be evaluated simultaneously, revealed genetic variati on for production of JH, sensitivity to JH, or sensitivity to social inhibi tion in five of six pairs, and potency of social inhibition in five of six pairs. There was often evidence for genotypic differences in more than one component, and no consistent pattern of association among any of the compon ents. Africanized bees had faster rates of behavioral development than Euro pean bees, but there were no racial differences in patterns of variation am ong the four components. These results indicate that there are at least sev eral, apparently distinct, physiological processes associated with JH and c olony age demography upon which natural selection can act to alter the rate of behavioral development in honeybees.