Abstract

Although "intrasexual selection" has been accepted as the mechanism by which males evolve elaborate secondary sexual traits which are used in aggressive contests, the importance of "intersexual selection" as a mechanism by which males have acquired exaggerated traits to display to females during courtship was less readily accepted. In spite of this scepticism, several genetic models have supported the latter idea, and many empirical studies showed that females were generally more discriminating in mate choice than males, because of differences in relative investment between sexes. Nowadays, this idea is reinforced by various concepts (parental investment, potential reproductive rate, environmental potential for polygamy...) which stress that the strength of sexual selection is related to many interdependent factors, such as mating systems, resource distribution (food, habitat, mate), life history and other ecological characteristics. The case of Salmonids is presented here to show how novel information on sexual selection has contributed to the understanding of the plasticity of breeding patterns in the context of evolutionary biology.