Cooperative Ecosystem Studies Unit, Gulf Coast CESU

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The U.S. Geological Survey (USGS) is offering a funding opportunity for a research project to develop population specific genetic markers for the diatom Didymosphenia geminata. The information will be used to determine the vectors and rate of introduction of this invasive aquatic species. USGS will provide assistance to academic institutions in carrying out their goals and objectives to develop new molecular markers and apply them to addressing diatom phylogeny. The collaborator will have the opportunity to resolve the phylogenetic relationships within the cymbelloid lineage of diatoms and evaluate the data in terms of the larger diatom lineage. The study will offer access to live algal material from the US and internationally for genetic sequencing. The objective of the project is determine rivering blooms of D. geminata are formed by an “invasive strain” that is common across the US, Europe and New Zealand. 1) Determine if genetic differences exist between the blooms from populations across North America, Europe and New Zealand. Laboratory investigations will screen genetic markers (nuclear, chloroplast and mitochondrial) for their reliability, ability to be amplified and variability across populations. ITS rDNA is quite variable, easy to amplify and has shown to be useful for population level studies both for freshwater. Additionally, microsatellite markers are widely used for analyzing genetic population structure and population relationships and will be evaluated. Multiple microsatellite loci have been developed for the marine diatoms Pseudonitzschia spp. and D. brightwelli. Recently, loci have been developed for the freshwater diatom Sellaphora capitata. Although very useful in green plants and animals, it is unclear whether mitochondrial and chloroplast markers can be used in diatoms. This is because the mode of transferring mtDNA and cpDNA through generations in diatoms is largely unknown. It is necessary that these genomes are uniparentally inherited so that matrilines can be established for inferring of ancestral history of populations. The results of this study should yield information on the potential of these molecules for resolving evolutionary relationships among populations of D. geminata. 2) Determine the relationships between bloom-forming populations of D. geminata across the United States.

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