THE USE OF MICROSATELLITE MARKERS TO COMPARE THE POPULATION STRUCTURE OF Pseudo-nitzschia pungens FROM THE PACIFIC NORTHWEST AND THE NORTH SEA

Nicolaus G. Adams¹, Lorenz Hauser², Russell P. Herwig², Gabrielle Rocap³, and Vera L. Trainer¹

¹NOAA-Fisheries, Northwest Fisheries Science Center, Seattle, WA, 98112, USA
²University of Washington, School of Aquatic and Fishery Sciences, Seattle, WA, 98195, USA
³University of Washington, School of Oceanography, Seattle, WA, 98195, USA

Pseudo-nitzschia pungens is a pennate diatom commonly found in the waters of the Pacific Northwest and the North Sea. Due to the frequency of domoic acid events in the Pacific Northwest an understanding of the population and bloom dynamics of Pseudo-nitzschia species in this region is needed. Our research compared various population genetic parameters of P. pungens isolated from the Juan de Fuca eddy region in the Pacific Northwest and from the North Sea. These data along with population differentiation statistics indicated that P. pungens from the Pacific Northwest had a different population structure than P. pungens from the North Sea. Genetic data from a North Sea P. pungens sample provided evidence for the presence of a single unstructured population while a more complex population structure was found in Pacific Northwest P. pungens samples. Microsatellite data indicated that two genetically distinct populations were present in all Pacific Northwest P. pungens samples. These results implied that either the two populations of P. pungens could have recently mixed in the Juan de Fuca eddy region but had not exchanged genetic material by sexual reproduction, or that there may be cryptic species (morphologically identical but reproductively isolated species). The detection of multiple populations or cryptic species of a potentially toxic diatom suggests a more complex cause of HABs in the Pacific Northwest than was hitherto assumed, and calls for additional studies investigating physiological and genetic differentiation between the two strains.