Conservation of aquatic biodiversity through molecular ecology
Bockrath, Katherine Diane
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Globally, aquatic biodiversity is in decline. Expanding demand for natural resources, habitat modification, and global climate change stress aquatic systems and as a result, many taxa are in decline. To slow the loss of biodiversity and to maintain current species richness, understanding how populations respond to environmental changes directly imposed by human activity is key. For this, molecular ecology is a useful tool and becoming the frontline in management. Using methods centered on information gathered through DNA- and RNA-based markers, the diversity and connectivity of populations – as well as inter-species dependencies – can be assessed. Additionally, by analyzing an individual’s gene expression patterns, their response to environmental stressors can be determined. I investigated imperiled taxa from two different aquatic systems. The first study investigates how freshwater mussels respond to human induced shifts in fish communities. Freshwater mussels require a fish host to complete their life cycle. Some mussels are generalists (using many different hosts) while others are specialists (using very few hosts). Identifying mussel larvae (glochidia) embedded within the gills of their fish hosts is difficult. Thus, I developed a mussel specific genetic barcode for identifying glochidia in the presence of overwhelming host DNA. Using genetic barcodes, I identify glochidia attached to fish to determine what mussels are using each fish species as a host, if any fish were an ecologically important host, and the environmental factors that promote mussel larvae finding a host. I found that generalist mussels use native fish species indiscriminately, but shifts in fish communities through habitat modification can cause generalist mussels to primarily associate with fish species previously absent before habitat modification occurred. In addition to freshwater mussels, the response of corals to stressors was assessed. Reef-building corals are critically imperiled due to diseases induced by rising sea-surface temperatures. In the US Virgin Islands, some Acropora palmata colonies are less susceptible to disease than others. To determine if there is a heritable basis for disease resistance, I used RNA-Seq to assess how corals differentially respond to disease. I found significant variation in gene expression across corals, but no differential expression that correlates to disease resilience.