DISSERTATION RESEARCH: Gametophyte Ecology: Consequences for the Distribution and Abundance of Tropical Ferns

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Ferns are unique among plants because they have two distinct, free-living stages in their life cycle. The sporophyte stage is the familiar frond-bearing plant, which asexually produces spores that germinate to form the gametophyte stage. The gametophyte, by contrast, is tiny and rarely visible, but it is key because it reproduces sexually to form the sporophyte and complete the life cycle of the fern. A fern sporophyte may disperse millions of spores into its environment, yet few gametophytes ever survive to complete the life cycle. Despite the importance of the gametophyte stage to the distribution and abundance of ferns, we know little about the factors that control its survival and reproduction. The goal of this research is to understand controls over survival and reproduction of fern gametophytes in the wet forests of Costa Rica, where ferns are an important component of the ecosystem. A series of observational studies and experiments will be used to determine how different species' gametophytes vary in their response to drought, light, and nutrient availability, and how these responses affect reproduction and the formation of sporophytes. This study will have application to the management and conservation of fern populations. The broader impacts of this research include support of a doctoral dissertation, development of a large collection of specimens that will be archived in the herbarium of the La Selva Biological Station, and the development of new techniques for measuring photosynthesis and nutrient uptake.