Evidence for the adaptive significance of enzyme activity levels: interspecific variation in alpha-GPDH and ADH in Drosophila.

The activity levels of alcohol dehydrogenase and alpha-glycerophosphate dehydrogenase were compared among nine species of Drosophila representing three phylogenetic groups. For any given life stage , interspecific variability in activity level was much greater for ADH than for d-GPDH. Patterns of ontogenetic expression of enzyme activity were also much more variable among species for ADH than for alpha-GPDH. These results are consistent with the interpretation that alpha-GPDH is involved with a relatively uniform adaptive function among species, whereas ADH levels may reflect variable adaptive capabilities. There is a significant correlation between ADH activities and survivorship on alcohol-treated media for these nine species.