Heritability and selection on body size in a natural population of Drosophila buzzatii

An attempt was made to assess whether the phenotypic differences in body size (as measured by wing length) between wild-caught mating and single Drosophila buzzatii males could be attributed to genetic differences between the samples. Mating males were found to be larger and less variable than a random sample of the population. The progeny of the mating males (produced by crossing to a random female from a stock derived from the same population) were on average larger than those of the single males, but not significantly so (P = 0.063), and less phenotypically variable. This difference in variance between the samples suggests that there are indeed genetic differences between the paternal samples but tests for significant differences in the additive genetic component of variance proved inconclusive. For both samples it was found that while the ratio of additive genetic variation in the laboratory to phenotypic variation in the field yielded estimates of ĥs2(N) congruent to 10% the regression of offspring reared in the laboratory on parents from the wild was not significantly different from zero. In addition, it was found that the average development time of the progeny of the mating males is shorter than that of the random sample.