Abstract
Developmental stability (DS) may confer an advantage in competition for mates. The present study tests this hypothesis using Drosophila immigrans, and proposes a novel approach to help broadly define the epigenetic factors causing such an effect. We first estimated the magnitude of isofemale heritability in sternopleural bristle fluctuating asymmetry (FA), using replicate genetic lines extracted from nature. Positional FA (PFA) exhibited significant among-line variation, and the heritability estimate of 0.10 (0.046 s.e.m.) was statistically significant. Among individual males, there was a significant positive relationship between PFA and copulation latency (time elapsed between introduction of females and copulation) and duration, but not copulation frequency. Moreover, high-DS lines exhibited significantly shorter copulation latency and duration compared with low-DS lines. When these components of sexual performance were again contrasted between lines with among-individual differences in bristle asymmetry controlled statistically, significant line effects on copulation latency and duration disappeared. The results suggest that deficits in the developmental apparatus underlying one particular trait can compromise individual sexual performance, and weaken the hypothesis that FA is a cue of overall 'genetic quality'.