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Unisexual, female- or male-biased populations are common among dioecious bryophytes and the demographic causes of such biases are unclear. Life history studies can be valuable in understanding the contribution of each life history stage to a population sex ratio, yet few studies use this approach. We chose to study the liverwort Marchantia infexa to investigate the potential effect of various stages/traits on population sex ratio. Across M. inflexa's distribution range, herbarium data suggest female-biased sex ratios. Field studies in Trinidad & Tobago suggest an overall 1:1 sex ratio within a single watershed, however, patches can be singlesex, bisexual or without sex expression. We investigated sex-specific survival of asexual propagules (lab), clonal expansive traits (greenhouse) and patterns of sex expression (field & greenhouse). We found that neither sex had a consistent advantage. Females had higher propagule survival, lower propagule production and higher growth rates. Sex expression tended to occur first in males then in females. These patterns suggest that focusing on any single stage or trait can result in erroneous conclusions as to the demographic causes of sex ratio biases. Thus, studies on population sex ratio biases should incorporate multiple traits and stages.

Populations of the desert moss Syntrichia caninervis Mitt. were sampled on a 1.5 hectare site in order to study spatial distributions of male, female, and mixed sex populations. Populations were also categorized in reference to their microhabitat (shaded versus exposed) and mapped on a coordinate grid system including prominent topographic trends. Exposed populations were found to be significantly clustered near trails and washes. Shaded populations, both mixed-sex and single-sex (female), were clumped in arrangement, but single-sex populations were more clumped than mixed-sex populations. This study provides a basis for exploring the potential mechanisms involved in the origins and maintenance of these patterns. We provide three potential explanations for these patterns: a leptokurtic hypothesis of spore dispersal, failure of the species to colonize new habitats via spores, and limitation of mixed-sex populations by the vegetative self-propagation of single-sex populations.

Plant-microbe interactions impact ecosystem function through nutrient cycling, community interactions, and individual costs/benefits to the organisms involved. However, information on the establishment, diversity, and function of plant-microbe interactions remains limited, especially for non-vascular plants. We hypothesized that variation in the environment and sex of a host plant, impact the composition and diversity of associated microbial communities. To test this hypothesis, we characterized the bacteriome of the non-vascular plant, Marchantia inflexa, in both males and females across multiple habitats by targeted sequencing of the bacterial 16S rRNA gene. We describe the bacteriome for M. inflexa, and find that it is abundant and diverse, showing some similarities with other non-vascular plant lineages. Using these data, we detected a habitat specific component of the bacteriome, and sex differences in the bacteriome under common garden conditions. On the basis of known microbial functions, our analyses suggest that the specific taxonomic assemblages of bacteria detected in particular habitat types may serve functional roles; allowing plants to better acclimate to their local environment, and that sex differences in the bacteriome may correspond to subtle differences in the physiology and morphology of the sexes. Our initial characterization of variation in bacteriome composition of this tropical liverwort lineage provides valuable information for better understanding the patterns of plant-microbe interactions across land plants. [ABSTRACT FROM AUTHOR]

The I Y i axis label should read I F SB v sb i / I F SB m sb i . Annals of Botany 118: 347-356, 2016 In the published manuscript the I Y i axis label of figure 6 is given incorrectly as I F SB v sb i / I F SB m sb i . [Extracted from the article]