Sideritis elica, from the Rhodope Mountains, is described as a species new to science. Results of a detailed morphological analysis were combined with the data of molecular analyses using DNA barcoding as an efficient tool for the genetic, taxonomic identification of plants. The combination of morphological features distinguishes the new species well: Its first three uppermost leaf pairs are significantly shorter and wider, the branchiness of the stems is much more frequent, the whole plant is much more lanate, and it looks almost white, as opposed to the other closed species of section Empedoclia, which look grayish green. The molecular analysis, based on the rbcL and trnH-psbA regions, supports the morphological data about the divergence of Sideritis scardica and Sideritis elica. The studied populations of the two taxa were found to be genetically distant (up to 6.8% polymorphism for trnH-psbA) with distinct population-specific nucleotide patterns, while no polymorphism in the DNA barcodes was detected within the Sideritis elica population. The results confirm the existence of a new species called Sideritis elica, which occurs in the nature reserve Chervenata Stena, located in the northern part of the Central Rhodope Mountains. There were only 12 individuals found in the locality, which underlines the necessity of conservation measures.
Keywords: cryptic species; medicinal plants; phenotypic variation; taxonomy.