Abstract
‘Good-genes’ models of sexual selection predict significant additive genetic variation for fitness-correlated traits within populations to be revealed by phenotypic traits. To test this prediction, we sampled brown trout (Salmo trutta) from their natural spawning place, analysed their carotenoid-based red and melanin-based dark skin colours and tested whether these colours can be used to predict offspring viability. We produced half-sib families by in vitro fertilization, reared the resulting embryos under standardized conditions, released the hatchlings into a streamlet and identified the surviving juveniles 20 months later with microsatellite markers. Embryo viability was revealed by the sires' dark pigmentation: darker males sired more viable offspring. However, the sires' red coloration correlated negatively with embryo survival. Our study demonstrates that genetic variation for fitness-correlated traits is revealed by male colour traits in our study population, but contrary to predictions from other studies, intense red colours do not signal good genes.
Highlights
Some ‘good-genes’ models of sexual selection predict that attractive males or males that are superior competitors in intrasexual selection are of high genetic quality and offer indirect genetic benefits to females ( Neff & Pitcher 2005)
The ideal species to test for genetic effects of sexual selection are those with no parental care, external fertilization and large family size, i.e. some frogs ( Welch et al 1998) and some fish species (e.g. Wedekind et al 2001, 2004; Rudolfsen et al 2005; Pitcher & Neff 2006)
MATERIAL AND METHODS Brown trout were collected from their natural spawning place in River Enziwigger in November by electrofishing
Summary
Some ‘good-genes’ models of sexual selection predict that attractive males or males that are superior competitors in intrasexual selection are of high genetic quality and offer indirect genetic benefits to females ( Neff & Pitcher 2005). Empirical tests of such models need to control for potentially confounding effects of, for example, differential female investment into embryos and juveniles (Parker 2003). Various non-exclusive types of costs have been discussed (Hadfield & Owens 2006) as follows: (i) the pigments are costly to acquire, e.g. because they are rare or owing to costly physiological handling (metabolism or transport), (ii) the pigments are required by other physiological processes, e.g. for immune functioning, or (iii) the pigments are toxic or the colours are dangerous, e.g. because they enhance conspicuousness to predators or they signal a social status that may need to be defended
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