Multivariate Post-copulatory Selection and Quantitative Genetics of Drosophila simulans Sex Comb

Abstract

This thesis is concerned with investigations into the influence of Drosophila simulans sex comb characteristics on male fertilization success. Sex comb is a complex trait that has length, depth, and tooth number. Predicting the outcome of selection on a complex trait comprising of several traits requires an estimation of the impact of selection on both traits variances and covariances. The influence of multivariate post-copulatery selection on Drosophila simulans sex comb components has been investigated where the effect of offensive and defensive bouts of selection on males sex comb have been estimated by scoring both the proportion of offspring fathered by the focal male when he is the first to mate with the female (P1), and proportion of offspring fathered by the focal male when he is the second to mate with the female (P2). The heritablities for all sex comb components as well as their underpinning G matrix were calculated. Although Drosophila simulans sex comb components were all significantly heritable, constraints have been found to affect the comb and impede its evolution as a response to post-copulatory sexual selection. These constraints arise mainly due to: 1) the absence of directional post-copulatory selection. 2) The positive genetic correlation between sex comb components. 3) Physical constraints. All of the above constraints could also explain the high additive genetic variance underlying D. simulans sex comb components.