Malate dehydrogenase phenotype, temperature and colony effects on flight metabolic rate in the Honey-bee, Apis mellifera

1. The 'fast' and 'medium' alleles of malate dehydrogenase (MDH-1) exhibit clines on three continents in Honey-bees (Nielsen, Page & Crosland 1994), suggesting that MDH-1 phenotype may have functional consequences. 2. To test the effect of MDH-1 phenotype on a relatively constant genetic and environmental background in Honey-bees, we compared slow-fast (SF) and slow-medium (SM) workers within two colonies containing medium-fast (MF) queens singly inseminated with semen from an (S) drone. Within each colony, all genes not tightly linked to MDH-1 should be randomly distributed among SM and SF workers. 3. SF bees had higher flight metabolic rates (MR) than SM bees at ambient temperatures of 21 °C and 38 °C, and higher wing-beat frequencies (WBF) at 21 °C. 4. There were also highly significant differences in MR of foragers from adjacent, similarly sized, related colonies, suggesting that there are other strong unexplained effects on flight MR. Flight MR and WBF decreased while thorax temperatures (T_th) increased as ambient temperature increased. 5. The data suggest that during high-intensity flight, Honey-bees reduce motor behaviour, either as a behavioural mechanism to prevent overheating or owing to direct inhibition of flight muscle metabolism by high T_th. 6. Our data and a previous study (Coelho & Mitton 1988) indicate a link between MDH-1 allozymes and flight metabolism in Honey-bees, supporting the contention that MDH-1 phenotype has functional metabolic consequences which may be subject to selection.