A preliminary phytogeographical analysis of inter- and intra-populational chloroplast DNA variation in Packera pseudaurea (Asteraceae: Senecioneae) from southwestern Alberta and adjacent Montana

Packera pseudaurea (Rydb.) Weber & Love has previously been identified as a species containing an unusually high level of chloroplast DNA (cpDNA) polymorphism. Proposed sources of this intrapopulational variation have included hybridization and introgression, either ongoing or resulting from migrations associated with past glacial events. Restriction site analysis was performed on individuals from seven populations of P. pseudaurea from southern Alberta and adjacent Montana to assess variation more precisely. High levels of intrapopulational polymorphisms comprising a total of nine different haplotypes, only one apparently unique to the species, were detected in all but one southern population. The haplotypes separate into two groups upon phylogenetic analysis, a separation that corresponds to that detected in a wider sampling of Packera species. With one or two exceptions, the haplotypes of one group are also found in species based west of the Rocky Mountains. Those of the other are found in species based all over North America. These results lend support to the hypothesis that the variation in P. pseudaurea originated when the ranges of different Packera species were brought together by glaciation.