A study was performed to determine intraspecific phylogenetic relationships between Arabidopsis thaliana ecotypes from widely separated areas of the world. Eighteen populations of Arabidopsis were studied using polymorphic DNA and morphologic analyses. Experiments were performed employing 15 microsatellite loci in 10 individuals from each of 18 Arabidopsis populations from four continents. Microsatellite loci were amplified by the Polymerase Chain Reaction, electrophoresed, sized, and the polymorphisms analyzed. Morphological studies were performed comparing 11 physical traits in 10 individuals from each population. It was found that: 1) the commonly held premise that North American Arabidopsis thaliana populations originated in Europe is supported; 2) although Asian populations examined appeared genetically distant from the European populations, the hypothesis that Arabidopsis originated in Asia requires additional examination; 3) the laboratory ecotype Kashmir may have originated in Europe, not India; and 4) Arabidopsis morphology has generally changed little among populations across the world.

Communicating Editor: Jim Manhart