Multivariate models of selection make explicit the influences of direct and indirect selection on the change in mean character value ofseveral traits (Arnold, 1988;Lande, 1979). Selection on a single character produces a direct response, the magnitude of which depends on the strength of selection and on the amount of additive genetic variance in that trait. Selection also produces indirect response on other traits; the magnitude of indirect response depends on the strength of selection and on the amount of additive genetic covariance between traits. When there is selection on each of several genetically correlated traits, response to selection is the sum of the direct and several indirect effects. These relationships are succinctly embodied in the multivariate formulation (Lande, 1979), M=GB.Abstract. -Estimates ofheritabilities and genetic correlations for seven reproductive attributes had previously been obtained from parent-offspring regression (Gromko, 1987. Copulation duration was shown to have a heritability of 0.23 and to be genetically correlated with courtship vigor (r A = -0.41) and with fertility (r A = 0.27). These observations form the basis for the prediction of direct and correlated responses to selection for increased and decreased copulation duration, which are reported here. The direct response corresponded closely to prediction, but the correlated responses did not provide consistent qualitative fit. A hypothesis is proposed to explain this difference in predictability of direct and correlated response to selection. The major postulate is that the different polygenes involved in the direct response to selection for copulation duration have different pleiotropic effects.

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Two genomic clones exhibiting a maternal-specific pattern of expression map to cytological region 52A. To elucidate the function of these clones we have undertaken a mutagenesis of the cytological region 51D-52A. This paper presents the results of this screen and the preliminary analysis of female-sterile and lethal mutations isolated. A total of twelve complementation groups have been identified, four of which are defined exclusively by female-sterile alleles. Only one visible mutation was isolated, a recessive temperature-sensitive allele of Thickened-arista (Tarts). Several of the seven lethal loci display an embryonic lethal phase. Three of the four female-sterile loci affect chorion structure with one resulting in underamplification of the chorion genes, and two (possibly three) of the four female-steriles affect nuclear division/DNA replication. Thus it appears that this is a "developmentally important" region, possibly representing a clustering of genes involved in either DNA replication or nuclear division.

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