Conserving on the edge: genetic variation and structure in northern populations of the endangered plant Dracocephalum ruyschiana L. (Lamiaceae)

Loss of biodiversity is accelerating, including the loss of genetic
diversity. Conservation of small, isolated populations may be important,
as they can provide valuable contributions to overall genetic variation
and long-term viability of species. Furthermore, such populations may play
an essential role in adaptation to new environments following changes in
e.g. land-use and climate. Dracocephalum ruyschiana is a threatened plant
species throughout its European distribution, but 25% of the European
populations are situated within Norway. Therefore, the species has its own
action plan in Norway, which includes demographic monitoring. However,
this monitoring does not cover genetic variation nor is the selection of
monitored populations based on genetic differentiation, therefore this
fundamental level of biodiversity is overlooked. We analyzed 43 sites
using 96 SNPs developed for D. ruyschiana, to investigate whether the
monitored populations cover the genetic variation and differentiation
found within the Norwegian distribution. The results show structuring and
differentiation between populations and indicate that there are at least
four distinct genetic groups, of which only two are covered extensively by
current demographic monitoring. We suggest that two sites representing the
two other genetic groups should be included in the national monitoring
program to better conserve the genetic variation found in the Norwegian
population of D. ruyschiana. Overall, our results highlight the importance
of an integrated, interdisciplinary framework to better monitor and
conserve biodiversity at several levels.