HERITABILITY AND SELECTION ON BODY-SIZE IN A NATURAL-POPULATION OF DROSOPHILA-BUZZATII

An attempt was made to assess whether the phenotypic differences in bo dy size (as measured by wing length) between wild-caught mating and si ngle Drosophila buzzatii males could be attributed to genetic differen ces between the samples. Mating males were found to be larger and less variable than a random sample of the population. The progeny of the m ating males (produced by crossing to a random female from a stock deri ved from the same population) were on average larger than those of the single males, but not significantly so (P = 0.063), and less phenotyp ically variable. This difference in variance between the samples sugge sts that there are indeed genetic differences between the paternal sam ples but tests for significant differences in the additive genetic com ponent of variance proved inconclusive. For both samples it was found that while the ratio of additive genetic variation in the laboratory t o phenotypic variation in the field yielded estimates of (h) over cap( s(N))(2) similar or equal to 10% the regression of offspring reared in the laboratory on parents from the wild was not significantly differe nt from zero. In addition, it was found that the average development t ime of the progeny of the mating males is shorter than that of the ran dom sample.