Within Coreopsis section Coreopsis (Asteraceae) both gradual and saltational modes of speciation are represented. Chloroplast DNA from both sets of diverging taxa will be digested with ten restriction enzymes, and the corresponding filters will be probed with eight cloned chloroplast DNA fragments. The diversity found within the three gradually diverging diploid morphological varieties of C. grandiflora will be used to determine whether divergence is occurring between the taxonomic varieties or between the two major, discontinuous geographical portions of its range. The presumed saltational speciation event involving C. nuecensoides and its derivative C. nuecensis will be examined to determine whether the relative amounts of chloroplast DNA diversity within the species correspond with a saltational event, and if so, how severe the accompanying population bottleneck may have been. A preliminary survey of cpDNA diversity has revealed considerable interspecific, interpopulational, and intrapopulational variation. The results of this study will give important insights into the genetic processes involved in two modes of speciation, and will demonstrate the usefulness of cpDNA for diversity analyses below the species level.
