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Abstract
Phytophthora ramorum populations in North America and Europe are comprised of three clonal lineages based on several different genetic marker systems (Ivors and others 2006, Martin 2008). Whether these lineages are ancient or a recent artifact of introduction has been unclear. We analyzed DNA sequence variation at five nuclear loci in order to better understand the evolutionary history of the three lineages and the relationships among them (Goss and others 2009). We did not see differences among isolates within each lineage, therefore the observed genetic divergence among lineages precedes introduction. Analysis with coalescent-based methods revealed that the lineages have been diverged for an evolutionarily significant period of time, roughly 165,000 to 500,000 years. Genes contained signatures of historical recombination between the lineages, indicating that ancestors of the
P. ramorum lineages reproduced sexually. The large genetic differences among lineages suggest that they were not introduced from a single interbreeding population. Instead, the three lineages likely originated from three different geographic locations such that they evolved in isolation from each other prior to introduction to North America and Europe.
Parent Publication
Citation
Goss, Erica M.; Larsen, Meg; Carbone, Ignazio; Givens, Donald R.; Chastagner, Gary A.; Grünwald, Niklaus J. 2010. Population Genetic Analysis Reveals Ancient Evolution and Recent Migration of
P. ramorum. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M. 2010. Proceedings of the Sudden Oak Death Fourth Science Symposium. Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 116-118
