The Valeriana officinalis aggregate in Sweden. A preliminary study.

Abstract

Common valerian (Valeriana officinalis L.) is a species of flowering plants native to Europe, the roots of which have been used in folk medicine for centuries. But due to high diversity in morphology and chromosome numbers, different populations in V. officinalis sensu lato have been variously treated as their own species, resulting in a complex taxon aggregate. A stable taxonomy with clearly delimited species is important for conservation biology since a species cannot be protected unless it has a name. It is also important for research into the evolution of potentially useful traits in groups of related species. Both of these positives are relevant in the case of plants in the V. officinalis aggregate due to their potential for plant-derived medicines. In Sweden, plants in the aggregate are classified into two species (V. officinalis sensu stricto, and Valeriana sambucifolia J. C. Mikan), with the latter being further split into two subspecies (subsp. sambucifolia, and subsp. salina). To test this hypothesis, we have performed a preliminary study using collected specimens stored in Herbarium GB. Due to constraints in time and resources no specimens from other herbaria were used, and only quantifiable morphological data was considered. Given that previous taxonomic research had focused on leaf morphology, this became the primary focus. This data was analyzed using the PCA method to summarize the variance amongst examined specimens. In addition, the localities in which the specimens had been collected were used to generate a distribution map for geographic and ecological data. Whilst the limited scope of the study makes the results inconclusive, we found evidence indicating that a taxon considered synonymous to V. officinalis sensu stricto (Valeriana baltica Pleijel) might represent a distinct species. Further research is needed and would require data from a larger number of specimens as well a molecular data.