Density dependence on male sexual expression in metapopulations of a tropical moss: a monoicous species almost dioicous

Abstract

Life-history variables such as reproductive allocation, sexual expression, sex ratio, and reproductive success, are central aspects of a species' ecology and evolution. For example, biases in male and female sex expression may play a large role in determining the viability of populations in the face of environmental pressures such as population fragmentation, climate change and habitat occupancy. Thus, in this study, we investigated reproductive traits in 10 metapopulations of Fissidens flaccidus Mitt. From each metapopulation, 30 patches were randomly selected, and samples were collected from each patch of 1cm2. A total of 20173 ramets were analyzed and classified into male, non-sporophytic female, sporophytic female, and non-sex expressing. In addition, population density in each patch was quantified. Our results showed that relative reproductive allocation in perigonia and sporophytes is greater than perichaetia. In addition, a trade-off between sexual relative reproductive allocation and asexual gemma production was observed, suggesting an important role of female ramets in asexual reproduction. The number of male ramets does not influence the reproductive success observed in each patch, and ramet density may induce male sex expression. Thus, we concluded that reproductive allocation in male function is efficient, since fewer male ramets can assure a considerable reproductive success. Furthermore, our results suggest that there may be a habitat preference between the sexes, since male ramets are found in patches with high density and mostly below female ramets, suggesting an avoidance of direct sunlight by male ramets.