Extended longevity in Drosophila is consistently associated with a decrease in developmental viability

It has proven relatively easy to select normal-lived strains of Drosophila for extended longevity in the laboratory. Long-lived strains have not been observed in the wild as yet. Of the various life-history traits that have b een investigated for their role in modulating the evolution of extended lon gevity, none have yet shown a consistent or convincing relationship. Other than developmental time, the traits usually investigated in this regard are those associated with the adult phase of the life cycle. We assayed develo pmental timing and viability in six pairs of normal- and long-lived strains , four pairs of which are from previously described strains and two pairs o f which are new strains that have been independently and recently selected. We find that the life-history trait most obviously associated with all our long-lived strains is a significantly reduced developmental viability, wit h the long-lived strains' having as much as twice the developmental lethali ty as do any of the normal-lived strains. The long-lived strains also pupat e closer to the food, a behavior known to decrease fitness. Thus the reduce d fitness of the long-lived strains appears to be due to both physiological and behavioral factors and may well explain why long lived strains are not usually found in the wild. The extension of longevity involves costs as we ll as benefits that, in this case, are borne by different individuals.