MAINTENANCE OF SEXUALLY DIMORPHIC PATTERNS OF GROWTH AND REPRODUCTION IN MARCHANTIA INFLEXA

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 among-population 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 asexua