DISSERTATION RESEARCH: The effects of dendritic structure on parasite metacommunities in stream networks

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Ecological communities are composed of many interacting species and provide valuable ecosystem services ranging from clean water to pollination. To maintain these ecosystem services, it is important to understand the processes that determine where, when and which species occur together. Dispersal, or the movement of organisms across the landscape, is an important process in determining what species exist at a specific site; however, the importance of dispersal is likely to vary for different types of organisms and for different habitats. To date, most research examining the role of dispersal has focused on habitats with distinct boundaries, such as forest fragments or ponds. The primary goal of this research is to explore the role of dispersal in structuring communities of wildlife parasites live in streams. A second goal of the research is to develop methods to use new DNA sequencing technologies to quantify the abundance of parasites in water samples, making it possible to rapidly survey parasite communities and identify areas of high and low infection. Streams and rivers can be important channels for the movement of pathogens, and this research will increase our understanding of infectious disease dynamics in freshwater ecosystems while also contributing new methods for assessing the distribution and abundance of freshwater parasites. Trematodes, also known as flukes or parasitic flatworms, are obligate endoparasites of mollusks and all classes of vertebrates. They have complex life cycles requiring multiple hosts, and because the hosts disperse at different spatial scales (e.g., fish vs. birds), they represent a valuable system for examining the role of dispersal in local community structure. This research will employ field surveys and molecular analyses to characterize trematode abundance and diversity within and across multiple stream networks in the southeastern U.S. Proceeding from mainstem to headwaters, investigators will quantify trematode infection in first-intermediate hosts (snails) from 15 sites within each stream network. As the obligate first-intermediate hosts of multiple trematode species, snails integrate information on the entire community of hosts involved in trematode life cycles. Investigators hypothesize that: i) there will be an increasing downstream gradient of overall trematode prevalence and diversity due to the continuous movement of free-living parasite stages and infected hosts downstream; and ii) that trematodes with mammalian or avian hosts will have a less pronounced downstream gradient of prevalence and diversity than those with fish hosts, due to greater host mobility across the landscape. By focusing on a diverse community of parasites that all use the same snail species as a first-intermediate host but that vary in vertebrate host use and thus dispersal potential, this research will provide new insights into the importance of dispersal in structuring local communities.