Sexual selection and reproductive behavior in the Cortez damselfish (Stegastes rectifraenum).
AuthorHoelzer, Guy Andrew.
AdvisorThomson, Donald A.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe evolutionary processes of sexual selection are investigated in this study by developing a new model for the evolution of epigamic traits and examining the effects of male-male competition, female choice and filial cannibalism in a field population of the Cortez damselfish (Stegastes rectifraenum). Two general processes have been proposed to explain the evolution of epigamic traits: the good genes process and the Fisherian process. A third process leading to the evolution of epigamic traits is presented here: the good parent process. Epigamic traits arise through this process by clarifying the differences in non-heritable parental quality among potential mates. A population genetic model is developed, which further suggests that increases in the frequency of good fathers in the population and phenotypic plasticity enhance the evolution of a good parent trait. The relative strengths of female choice and male-male competition were studied in S. rectifraenum by direct observation of reproductive behavior, and through field experiments. Male body size was found to be the single most important correlate of male reproductive success. Males were removed from their territories to determine the extent to which the vacant territories were valued by other local males. All of the territories were quickly recolonized by new males and sites that initially showed the highest reproductive success continued to be the most successful when new residents were present. A second experiment involved standardizing nests in 30 territories. Under these conditions male body size was no longer correlated with reproductive success, indicating that females are strongly influenced by variance in natural nest sites. Consequently, male-male competition over territories containing high quality nest sites, in combination with female choice of those sites, generates the observed correlation between male body size and reproductive success. Partial clutch filial cannibalism by male S. rectifraenum was studied in the same population. A group of custodial males were fed eggs, while controls remained unfed. Both groups were dissected on the next day to determine the number of eggs in their stomachs. Fed males had significantly fewer eggs in their guts, indicating that they indeed feed on the eggs they guard, rather than take them incidently during nest maintenance activities. A second egg feeding experiment showed that male behaviour and reproductive success are little affected by filial cannibalism; thus it is hypothesized that the energy gained by this behaviour is channelled primarily into growth and survival.
Degree ProgramEcology & Evolutionary Biology