Measures of fitness in Drosophila : (population genetics, Drosophila, fitness, natural selection)

Ten proposed experimental measures of fitness in Drosophila have been estimated in 8 to 38 strains of D. melanogaster with 1 to 6 replications in order to assess the degree of association among the measures. One measure is a composite of the classical fitness components viability, fecundity, and mating speed. Two tests--the Knight-Robertson method and the compound-autosome method--are based on intraspecific competitive ability; three tests are based on interspecific competitive ability with D. simulans, D. mauritiana, or D. ananassae; two measures are based on the productivity and biomass of equilibrium populations; and two measures are based on the dynamics of change in frequency of a balancer chromosome in experimental populations. The tests fall into four groups with significant correlations among tests within a group but weaker or nonsignificant correlations between groups. The first group consists of the composite index and the two intraspecific tests. We infer that these methods measure attributes strongly allied with classical darwinian fitness. The second group consists of the interspecific tests, which apparently emphasize somewhat different characteristics than those associated with darwinian fitness. The third group consists of the measures based on productivity or biomass of equilibrium populations, and these measures may be allied with Wright's mean selective value, although this interpretation is speculative. The fourth and final group consists of the measures resulting from changes in chromosome frequency in experimental populations. Each group of tests measures distinct characteristics that are probably important in particular contexts, but only the intraspecific tests correspond to darwinian fitness.Daniel L . Hartl and David S. Haymer, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri