(Møller& Pomiankowski 1993; Johnstone 1996). Such redundant signals may not be current targets of intrasexual selection,instead resulting from the accumulation of traits that previously conferred an advantage in male contests or in a different context. Identifying traits that currently confer an advantage in contest competition is thus necessary to understand the evolution of male trait variation and multiple male ornaments.Size and ornamentation often predict the outcome of male–male contests in species in which these traits are larger or more exaggerated in males (Andersson 1994).Most studies of intrasexual selection have examined traits
that show male-biased dimorphism because these are expected a priori to be targets of sexual selection. However,traits that are monomorphic or are more exaggerated in females may also play a role in male–male contests (Maklakov et al. 2004; e.g. Legrand & Morse 2000; Prenteret al. 2003; Kraaijeveld et al. 2004). In several species of arthropods
in which females are larger than males, larger
size is advantageous in male contest competition (Fairbairn
& Preziosi 1994; Kraushaar & Blanckenhorn 2002;
Prenter et al. 2003; Maklakov et al. 2004). In contrast, in
yellow-pine chipmunks, Tamias amoenus, one of relatively
few mammals with female-biased sexual size dimorphism
(Møller& Pomiankowski 1993; Johnstone 1996). Such redundant signals may not be current targets of intrasexual selection,instead resulting from the accumulation of traits that previously conferred an advantage in male contests or in a different context. Identifying traits that currently confer an advantage in contest competition is thus necessary to understand the evolution of male trait variation and multiple male ornaments.Size and ornamentation often predict the outcome of male–male contests in species in which these traits are larger or more exaggerated in males (Andersson 1994).Most studies of intrasexual selection have examined traitsthat show male-biased dimorphism because these are expected a priori to be targets of sexual selection. However,traits that are monomorphic or are more exaggerated in females may also play a role in male–male contests (Maklakov et al. 2004; e.g. Legrand & Morse 2000; Prenteret al. 2003; Kraaijeveld et al. 2004). In several species of arthropodsin which females are larger than males, largersize is advantageous in male contest competition (Fairbairn& Preziosi 1994; Kraushaar & Blanckenhorn 2002;Prenter et al. 2003; Maklakov et al. 2004). In contrast, inyellow-pine chipmunks, Tamias amoenus, one of relativelyfew mammals with female-biased sexual size dimorphism
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