NUMEROUS CHLOROPLAST DNA POLYMORPHISMS ARE SHARED AMONG DIFFERENT POPULATIONS AND SPECIES IN THE AUREOID SENECIO (PACKERA) COMPLEX

Species boundaries within the aureoid Senecio complex (Packera) are po orly defined, possibly as a result of hybridization and introgression. The results of restriction site analysis of cpDNA using 16 enzymes an d hybridization with lettuce probes representing over 95% of the chlor oplast genome reveal a high level of intrapopulational polymorphism co mbined with a relatively low level of interspecific variation. Forty-n ine populations representing 23 different species were examined, and o nly 20 variable restriction sites were identified. Eleven of the 20 va riable sites were polymorphic in at least one population, and 14 of th e 23 species were polymorphic for at least one site. The polymorphisms are widespread and are found in species representing all of the previ ously recognized subgroups of the aureoid complex. Individuals analyze d separately were shown to possess only a single haplotype. Although t he polymorphisms may be the result of hybridization and introgression, it is difficult to explain the geographical patterns based on the cur rent distribution of species. It is possible that the aureoid complex represents a single, polymorphic biological species.