Generation and maintenance of diversity of life history and sexual systems

Unlike vascular plants, in mosses it is the gametophyte that is long-lived and the ephemeral sporophyte is physically dependent upon it. Sex organs are expressed in the gametophyte stage and controlled by a non-recombining sex chromosome pair; a unique chromosome in each sex. Although a balanced sex ratio based on sex chromosomes (genotypic sex) is expected in spores after meiosis, S. caninervis is notable for its extremely strong sex ratio bias, often with more than 10 females for every one male, based on the presence of sex organs (phenotypic sex). In most populations, more than 80% of the individuals do not produce sex organs and thus their genotypic sex and the true population sex ratio are obscured.