Disruptive selection for sternopleural bristle phenotypes inDrosophila ananassae

Abstract

Disruptive selection is potentially critical in maintaining variation and initiating speciation and plays an important role in the organization of genetic variability in natural populations. It occurs when extreme phenotypes have a fitness advantage over intermediate phenotypes. Disruptive selection for high and low numbers of sternopleural bristles in Drosophila ananassae was applied for 12 generations to test its effect in induction of behavioural isolation. Pattern of mating between flies of high and low lines was tested in an Elens–Wattiaux mating chamber by using a multiple-choice technique after G5and G12. Data was analyzed by calculating χ2under the assumption of random mating to test the difference between homo- and heterogamic matings, and sexual isolation was tested by calculating the isolation estimate. The results show that there is no evidence for sexual isolation in G5and G12. The realized heritability, standard error of regression coefficient, and t values suggest that disruptive selection for sternopleural bristle phenotypes was effective, but it does not lead to behavioral isolation in D. ananassae. Rather, it induces differences in mating propensity, which is influenced by sternopleural bristle phenotypes.