Molecular Markers Show How Pollen and Seed Dispersal Affect Population Genetic Structure in Coast Live Oak (Quercus agrifolia Née)1 (original) (raw)
Coast live oak (Quercus agrifolia Née) occurs in the coast range mountains from southern Mendocino County, California, to the Sierra San Pedro Martir, Baja California, Mexico. In Northern and Central California, coast live oak is suffering heavy mortality as a result of infection by Phytophthora ramorum. Earlier studies indicated biochemical differentiation of central coast populations from those of Northern and Southern California, an important hybrid zone in Northern California. A possible differential response to inoculation between populations from Northern and Southern California has also been reported. Here, we report results of a rangewide genetic diversity study of this species using chloroplast and nuclear microsatellite markers. The chloroplast genome is inherited maternally and its dispersal is limited because of the relatively large heavy seeds of oaks. We analyzed chloroplast microsatellites in more than 500 individuals from 41 populations and nuclear microsatellites in about 500 individuals from 28 populations of coast live oak from throughout its range. Based upon the chloroplast haplotype distributions, at least four biogeographic groups were detected. Nuclear microsatellite markers revealed reduced levels of genetic structure as a result of pollen dispersal. We discuss the roles of seed and pollen dispersal in the evolution of populations of coast live oak and how this information may help in developing strategies for studies of resistance to the sudden oak death disease.
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