Abstract
Recent theory predicts that males should choose social environments that maximize their relative attractiveness to females by preferentially associating with less attractive rivals, so as to enhance their mating success. Using the Trinidadian guppy (Poecilia reticulata), a highly social species, we tested for non-random social associations among males in mixed-sex groups based on two phenotypic traits (body length and coloration) that predict relative sexual attractiveness to females and sexual (sperm) competitiveness. Based on a well-replicated laboratory dichotomous-choice test of social group preference, we could not reject the null hypothesis that focal males chose randomly between a mixed-sex group that comprised a female and a rival male that was less sexually attractive than themselves and another mixed-sex group containing a sexually more attractive male. The same conclusion was reached when females were absent from the two groups. As might be expected from these laboratory findings, free-ranging males in the field were not assorted by either body length or colour in mixed-sex shoals. The apparent lack of an evolved and expressed preference in wild male guppies from our study population to form social associations with other males based on their relative sexual attractiveness and competitiveness might be due to the fission-fusion dynamics of guppy shoals in nature. Such social dynamics likely places constraints on the formation of stable phenotype-based social associations among males. This possibility is supported by a simulation model which assumes group departure rules based on relative body size and coloration in males.
Highlights
Animal societies are commonly structured into social groups or networks of non-randomly interacting individuals that preferentially associate with certain social partners, and avoid others, based on their particular phenotypic traits [1,2,3]
Guppies in nature live in mixed-sex, highly promiscuous, fission-fusion social groups [21, 22, 26,27,28]
Contrary to our a priori prediction, male guppies from the low-predation Upper Aripo River population in Trinidad did not exhibit an association preference for a mixed-sex shoal containing a less attractive male sexual rival over another nearby mixed-sex shoal containing a more attractive male rival when given a dichotomous choice in the current study
Summary
Animal societies are commonly structured into social groups or networks of non-randomly interacting individuals that preferentially associate with certain social partners, and avoid others, based on their particular phenotypic traits [1,2,3]. Individuals can effectively modify their immediate social environment or create social niches, which in turn may influence the selection regime they experience and their fitness [4,5,6,7,8]. Male Sexiness and Social Associations in the Guppy PLOS ONE | DOI:10.1371/journal.pone.0151243 March 17, 2016
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