Conservation Biology of the Rare and Threatened Drymocallis rupestris - A Study of Genetic Variation, Seed Germination and Self-fertility

Studying the ecology and measuring levels of population genetic diversity are important steps for assessing the conservation status and implementing appropriate conservation strategies for rare or endangered plant species. The Norwegian populations of Drymocallis rupestris, a perennial plant in the Rosaceae family, are critically endangered and limited to only a few locations around the Oslo fjord. Samples from these populations were investigated using SNP markers, generated by ddRADseq, to determine levels and structure of genetic variability. To allow for comparisons the Norwegian samples were compared to individuals of cultivated origin and samples from Sweden. Two separate seed germination experiments and a self- fertility test was conducted in order to assess the viability of seeds. Results showed that the genetic variability varied within each population, and there was no correlation between large populations having more diversity than small. Each of the Norwegian populations were genetically distinct from the samples of cultivated origin and generally showed high differentiation between each other. Two localities from the same peninsula in Asker (Akershus) showed low genetic differentiation, the same did the population from Jeløya and the Swedish population. Several of the populations showed signs of inbreeding, whereas others did not, but did in turn have low genetic variation. Results from the self-fertility experiment suggested that the species in self-incompatible. Overall, the low genetic diversity, inbreeding and limited germination of dark grown seeds could indicate low viability for the remaining Norwegian populations of D. rupestris, and a close conservation management is recommended.