Chloroplast DNA diversity is low in a wild plant, Lupinus texensis

Chloroplast DNA diversity was measured in an annual flowering plant, Lupinus texensis. Individual plants were collected from 21 local populations throughout the range of the species in Texas. Chloroplast DNA was isolated separately from each plant and digested with seven restriction enzymes. The most common form of the 150-kilobase-pair genome was cut at 134 sites, so that about 0.5% of the base pairs in the genome were sampled. Of the 100 plants examined, 88 had identical restriction fragment patterns. Three variant forms were found in different local populations. Two, represented in single plants, differed from wild type in the presence or absence of single restriction sites. The third variant was fixed in one of the local populations; it had lost a restriction site and also had a deletion of approximately equal to 100 base pairs. The data suggest that chloroplast DNA in this plant is much less polymorphic than mitochondrial DNA from animals and is probably less polymorphic than nuclear genes in the same plant or in animals.