Genetic basis of sexual dimorphism in the threespine stickleback Gasterosteus aculeatus

Sexual dimorphism (SD) in morphological, behavioural and
physiological features is common, but the genetics of SD in
the wild has seldom been studied in detail. We investigated
the genetic basis of SD in morphological traits of threespine
stickleback (Gasterosteus aculeatus) by conducting a large
breeding experiment with fish from an ancestral marine population
that acts as a source of morphological variation. We also
examined the patterns of SD in a set of 38 wild populations from
different habitats to investigate the relationship between the
genetic architecture of SD of the marine ancestral population
in relation to variation within and among natural populations.
The results show that genetic architecture in terms of heritabilities,
additive genetic variances and covariances (as well as
correlations) is very similar in the two sexes in spite of the fact
that many of the traits express significant SD. Furthermore,
population differences in threespine stickleback body shape
and armour SD appear to have evolved despite constraints
imposed by genetic architecture. This implies that constraints
for the evolution of SD imposed by strong genetic correlations
are not as severe and absolute as commonly thought.