title: The sexual selection paradigm: have we overlooked other mechanisms in the evolution of male ornaments?
abstract: Extravagant male ornaments expressed during reproduction are almost invariably assumed to be sexually selected and evolve through competition for mating opportunities. Yet in species where male reproductive success depends on the defence of offspring, male ornaments could also evolve through social competition for offspring survival. However, in contrast to female ornaments, this possibility has received little attention in males. We show that a male ornament that is traditionally assumed to be sexually selected--the red nuptial coloration of the three-spined stickleback--is under stronger selection for offspring survival than for mating success. Males express most coloration during parenting, when they no longer attract females, and the colour correlates with nest retention and hatching success but not with attractiveness to females. This contradicts earlier assumptions and suggests that social selection for offspring survival rather than for sexual selection for mating success is the main mechanism maintaining the ornament in the population. These results suggest that we should consider other forms of social selection beyond sexual selection when seeking to explain the function and evolution of male ornaments. An incorrect assignment of selection pressures could hamper our understanding of evolution.
authors.affiliation: Department of Biosciences, University of Helsinki, PO Box 65, 00014 Helsinki, Finland ulrika.candolin@helsinki.fi.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Candolin
authors.affiliation: Department of Biosciences, University of Helsinki, PO Box 65, 00014 Helsinki, Finland.
authors.forename: Iina
authors.initials: I
authors.lastname: Tukiainen
mesh_terms: D000374:Aggression; D000818:Animals; D005075:Biological Evolution; D003116:Color; D008297:Male; D052586:Mating Preference, Animal; D009425:Nesting Behavior; D010858:Pigmentation; D012727:Sex Characteristics; D023701:Smegmamorpha / Q000502:physiology*
keywords: mate choice; offspring survival; parental care; signals; social selection