Genetic variation in the endemic plants of the Athabasca sand dunes: Origin, evolution, and implications for conservation

In this study, we compared the genetic variation within and among populations of five endemic plant taxa from the Athabasca sand dunes in northern Saskatchewan, Canada, with the related geographically widespread species from which they are thought to have evolved. The results largely conformed with theories and empirical evidence that suggest restricted species have less genetic variation than widespread species. Stellaria arenicola and Deschampsia mackenzieana have evolved while sympatric with populations of their progenitor species and were found to have less population genetic variation than the widespread species. The tetraploid nature of Deschampsia mackenzieana isolated it from the adjacent diploid gene pool of Deschampsia cespitosa. In contrast, Stellaria arenicola can still hybridize with its progenitor, Stellaria longipes, though a shift to higher levels of inbreeding may have aided the evolution of this endemic. Evidence suggests these endemics have evolved from the sympatric gene pool of the progenitor species. Salix silicicola and Armeria maritima subsp. interior, two endemics that have evolved from allopatric arctic progenitors, were found to have less genetic variation than their related widespread taxa. Evidence suggested heterozygosity confers a fitness advantage in the progenitor Salix alaxensis, whereas in Salix silicicola, a heterozygote deficiency may be due to directional selection or inbreeding. Only one locus in one population was polymorphic in Armeria maritima subsp. interior, perhaps the rarest endemic on the Athabasca sand dunes, though populations of the progenitor, Armeria maritima subsp. labradorica were found to have little genetic variation as well. The endemic Achillea millefolium subsp. megacephala, was found to have more genetic variation than the widespread progenitor, Achillea millefolium subsp. lanulosa. All of the endemic species had high genetic identity with progenitor populations, regardless of the sympatric or allopatric nature of their respective distributions. These data support previous suggestions that the endemics have evolved on the Athabasca sand dunes during the Holocene. Conservation recommendations were made for preserving the endemic plants and their genetic diversity in light of the information provided from this study.