Phylogeograpy and population structure in Dryas octopetala L. analysed by microsatellite markers

Abstract

Dryas octopetala L. is an arctic-alpine plant that belongs to a genus where the number and delimitation of species are not fully resolved. The plant is unusual, compared with most other arctic-alpine plants in its diploid, dwarf-shrub habit with slow generation turnover. In this study, ten newly developed microsatellite markers have been tested and used to infer both phylogeography and population structure in 471 individuals of D. octopetala sampled from seven main localities in the North Atlantic area. In addition, the microsatellite markers were used to investigate whether there is genetic support for assigning three morphotypes of D. octopetala on Svalbard to taxa, as previously proposed by Russian scientists. Nine of the ten microsatellites were analysed in this study, and provided a resolution high enough to distinguish between individuals. At a phylogeographic scale, the analysed material grouped into three main groups, a southern group, an intermediate group and a northernmost group. It is likely that there have been two main colonization routes following the glacial retreat in the North Atlantic region, one southern and one eastern. This study supports a colonization route from the south for the southern Norwegian populations, while an eastern immigration route probably has colonized Greenland, northern Norway and Svalbard. At a smaller, population scale, the microsatellites separated between different genets of D. octopetala. The local D. octopetala populations were mainly in Hardy-Weinberg equilibrium and no latitudinal trend was found regarding the proportion of ramets in the sampled populations or for heterozygote deficiency. No evidence for assigning the three morphotypes occurring on Svalbard to taxa was found, and thus this study concludes that there is only one Dryas species on Svalbard, i.e., D. octopetala.