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Title: Clonal population structures are derived from various population processes in the protistan oyster parasite Perkinsus marinus

item THOMPSON, PETER - University Of Maryland
item Rosenthal, Benjamin
item HARE, MATTHEW - Cornell University

Submitted to: Journal of Eukaryotic Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2010
Publication Date: 5/1/2011
Citation: Thompson, P.C., Rosenthal, B.M., Hare, M.P. 2011. Clonal population structures are derived from various population processes in the protistan oyster parasite Perkinsus marinus. Journal of Eukaryotic Microbiology. 11(3):598-609.

Interpretive Summary: A pioneering study of genetic variation in populations of an important parasite of oysters has established that this parasite disseminates as a series of clones, each demarcated by a suite of genetic characteristics, rather than as a population of freely interbreeding individuals. This insight sheds light on the epidemiology of Dermo disease in the easter oyster, Crassostrea virginica.

Technical Abstract: Population genetic analysis of genotypes comprised of seven microsatellite loci revealed clonal genetic patterns in each of four populations of the protistan estuarine parasite Perkinsus marinus. Each locus was amplified directly from DNA extracted from infected oysters collected from four geographic locations, ranging from Florida to Massachusetts, over two seasons. Of 274 infected oysters, 129 (54%) harbored infections of solely one parasite genotype; these were subjected to population genetic analyses. Significant deviations from Hardy-Weinberg Equilibrium and significant multilocus linkage disequilibrium were detected in most sampled populations, consistent with clonality in P. marinus populations. Particular genotypes were identified more than once in two populations, indicating asexual reproduction can occur. Substantial heterozygote deficits were evident in three populations, suggesting the occurrence of inbreeding when sexual reproduction occurs. In contrast, significant heterozygote excess characterized one population where a particular multilocus lineage predominates. These clonal genetic patterns suggest that over short periods of time, selection may act upon independent parasite lineages, rather than a cohesive, interbreeding population of individuals. Nevertheless, the potential for outcrossing exists in P. marinus populations, which may result in the evolution of parasite populations over longer periods of time.