A Mediterranean medicinal plant in the continental Balkans: A plastid DNA-based phylogeographic survey of Salvia officinalis (Lamiaceae) and its conservation implications

Abstract

Salvia officinalis (Lamiaceae), common or Dalmatian sage, is a Mediterranean aromatic and medicinal plant used in medicine since ancient times. Knowledge on current genetic patterns and genealogical history of its natural populations is required for both breeding efforts and species conservation. We used sequences of two chloroplast intergenic spacers, 3'rps16-5'trnK and rp132-trnL, from 83 individuals from eight natural populations to distinguish between anthropogenic vs natural origin of four disjunct inland populations found outside of the main Adriatic range of the species. We found seven haplotypes, high total gene diversity (H-r = 0.695) and genetic differentiation (G(ST) = 0.682), as well as a phylogeographic structure with two lineages, a sub-structured inland-Adriatic lineage (IAL, comprising inland and Adriatic sub-lineages) and a purely Adriatic lineage (PAL). All four inland and disjunct populations, which comprised the inland sub-lineage of IAL, were almost fixed for a distinct haplotype genealogically closely related to the ancestral haplotype and displayed other features of relict populations. Along with previous biogeographic data and other lines of evidence, assumptions on their anthropogenic origin were rejected. At present, a less diverse IAL (Hd = 0.426, pi = 0.00106) and a more diverse PAL (Hd = 0.403, pi = 0.00257), whose divergence was dated to the Pliocene (3.267 Mya), do not exhibit signs of recent demographic expansions and overlap on the SE Adriatic coast, a region delineated as the main glacial refugium of S. officinalis. Conservation measures accounting for the historical distinctiveness of populations and focusing on currently the most threatened populations are recommended.