Shifts in Myxomycete Community Structure in Selected Microhabitats Across Nutrient Treatments in a Lowland Tropical Forest of Panama

Myxomycetes (plasmodial slime molds) are abundant amoeboid predators of bacteria and other microorganisms. They are found worldwide, largely in association with decaying plant material in terrestrial habitats. Their consumption of bacterial prey puts microbial predators such as myxomycetes in a key position in various ecosystem processes wherein they help regulate the flow of nutrients (e.g., N and C) through the ecosystem. The importance of microbial predators in nutrient cycling and plant productivity is well established. Given the extent to which tropical ecosystems influence global nutrient fluxes, along with the ecologically significant role that myxomycetes play in these processes, there is a pressing need to learn more about this understudied community. This dissertation comprises an important first step toward developing an understanding of the ecological role of myxomycetes, with two major contributions. Identifying species is a fundamental step toward characterizing the diversity of a community. Given the unique challenge of identifying species of myxomycetes imposed by their unique biology, this dissertation begins in chapter two with a review of the myxomycete species concept. The various species concepts used (or potentially used) to identify species of myxomycetes are discussed. In chapter three, the challenges that myxomycete identification pose are described in the context of an ecological study. Therein, the use of a long-term nutrient fertilization experiment is described within which the effects of three major macronutrients, N, P and K on the myxomycete community in a lowland tropical forest of Panama are investigated. Interestingly, very little evidence supports the presence of a nutrient limitation to the myxomycete community, despite the many limitations that have been identified for other groups in this ecosystem (e.g., plants). The unexpected results provide the opportunity to again discuss the complications of species identification and enumeration of myxomycetes for in-depth studies. The results also highlight the unique biology of myxomycetes and provide new insights into their ecology. Finally, in chapter four, a holistic approach is employed to describe a species new to science that was discovered during the course of this dissertation work in Panama. Overall this dissertation highlights the importance of myxomycete taxonomy in an ecological framework