Inbreeding Affects Female Preference for Symmetry in Computer-Animated Sticklebacks

Fluctuating asymmetries are small random deviations from perfect symmetry in bilateral traits caused by the inability of individuals to cope with stress during development. The degree of asymmetry of secondary sexual characters is supposed to convey information about a male's phenotypic and/or genetic quality, and females are thus expected to use bilateral symmetry as a cue in mate choice. We offered female three-spined sticklebacks (Gasterosteus aculeatus L.) that had been inbred for one generation and outbred control females the choice between computer-animated male models differing exclusively in the symmetry of their pelvic spines. Inbred females exhibited a significantly stronger preference for the symmetric model than outbred females, suggesting that females of relatively poor quality are more prepared to pay the costs of choosiness and obtain higher marginal benefits from their discrimination than females of better quality.