Genetic diversity in the tetraploid sand dune endemic Deschampsia mackenzieana and its widespread iploid progenitor D. Cespitosa (Poaceae)

Electrophoretic variation was examined in 14 populations of tetraploid Deschampsia mackenzieana, an endemic of the Athabasca sand dunes in northern Saskatchewan, Canada, and 20 populations of its geographically widespread diploid progenitor, D. cespitosa. Three of the D. cespitosa populations were sympatric with the endemic on the Athabasca sand dunes. Populations of the endemic were found to have fewer alleles per locus (1.22 vs. 1.52), fewer alleles per polymorphic locus (2.17 vs. 2.70), lower percent polymorphic loci (18.9 vs. 30.5), and lower heterozygosity (0.062 vs. 0.119) than progenitor populations. Species level genetic diversity parameters also indicated that D. mackenzieana was genetically depauperate relative to its progenitor D. cespitosa. Deschampsia mackenzieana had no novel alleles but did share one allele with sympatric progenitor populations that did not occur in populations of D. cespitosa from other habitats. Although both species were found to partition most of their genetic diversity within populations, D. mackenzieana did have more of its limited genetic diversity partitioned among populations than D. cespitosa. The close genetic relationship between D. mackenzieana and sympatric populations of D. cespitosa may suggest the endemic tetraploid evolved from the sympatric diploid gene pool in the Athabasca sand dune region. The low levels of genetic diversity in D. mackenzieana suggest a restricted origin with limited gene flow from the progenitor since speciation.