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Please use this identifier to cite or link to this item: http://hdl.handle.net/10225/138

Authors: Fuselier, Linda Catherine
Keywords: Bryophyte
sexual dimorphism
Date Created: 2004
Publisher: University of Kentucky
Abstract: Sexual dimorphism in life history traits may influence the distribution of the sexes, population sex ratios, the maintenance of sex in populations, and the evolutionary potential of a species. In bryophytes, sexual dimorphism in traits related to growth and reproduction may be responsible for female-biased population sex ratios and a lack of sexual reproduction. I examined the roles of natural selection in maintaining sexual dimorphism in the context of impacts on bryophyte population sex ratios, using Marchantia inflexa as a model system. My studies included an assessment of amongpopulation variation in habitat use by the sexes, comparison of phenotypes between single-sex and both-sex populations, a field study of natural selection, and a comparison of the influence of selection on asexual and sexual fitness components. The sexes of M. inflexa were sexually dimorphic in investment in growth, asexual and sexual reproduction. The sexes were spatially separated in populations, but the sexes overlapped in habitat use. Populations differed in growth, asexual reproduction rates, degrees of sexual dimorphism, and strength of among-trait correlations. Plants from single-sex and both-sex populations differed in investment in growth and asexual reproduction, but the two population types showed the same degree of sexual dimorphism. Thus, local environment may be more influential than the presence of the opposite sex in maintaining sexual dimorphism. Selection on sexually dimorphic traits was both sex-specific and environmentally dependent. Between-sex correlations were not significant in the greenhouse but were significant in the field thus, evolution and expression of sexual dimorphism in nature may be constrained by among-trait and between-sex correlations. Additionally, females incurred a cost of plasticity that males did not. Because there was a negative trade-off between sexual and asexual fitness, overall lifetime selection may result in a different picture of how the sexes experience selection. The combination of sex-specific and environment-dependent selection, and sex-specific costs to plasticity may not only maintain sexually dimorphic traits but also ensure the persistence of both sexes in a population.
URI: http://hdl.handle.net/10225/138
Appears in Collections:Electronic Theses and Dissertations

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