Revisiting the age-old debate on fluctuating asymmetry and sexual selection

SemIDEEV
 20/11/2026
 12:00:00
 Roshan Kumar VIJENDRAVARMA (IRBI- CNRS)
 IDEEV - Salle Rosalind Franklin

The developmental instability-sexual selection hypothesis postulates fluctuating asymmetry (FA) in individuals as a readout of their developmental instability, and that it is thus a reliable cue to assess the genetic quality of potential mates and competitors. Innumerable studies across the taxa have tested this hypothesis over the last four decades, but the experimental data is heterogeneous and largely inconclusive. The hypothesis remained a highly controversial topic in biology with several criticisms levied against it. The observed heterogeneity in the vast amount of empirical data, is biologically relevant and needs to be understood. By revisiting this empirical data, I propose a new theory that re-establishes the idea that FA is indeed a target for sexual selection; explains satisfactorily the heterogeneity in data so far; and addresses the criticisms levied against some postulates of the original hypothesis. Using Drosophila melanogaster, a species wherein females identify symmetric males through their song and preferentially mate with them, I empirically validate this new theory.