Phylogeography of Swertia perennis in Europe based on cpDNA markers

Abstract

Background. Swertia perennis (Gentianaceae) is a perennial diploid and clonal plant species found discontinuously distributed in the peat bogs in mountains of Europe, Asia and North America as well as in European lowlands. The current geographical dispersion of S. perennis is probably an effect of Quaternary climatic changes that played an important role in determining the present-day distribution of Swertia and numerous other plant and animal species.

Methods. A presented survey of molecular studies based on combined data from chloroplast DNA markers (trnL-trnF and trnH-psbA) that were conducted to elucidate the phylogeography of S. perennis in European localities. Plants were collected from 28 populations that represent different localities in lowlands as well as in mountain areas of Europe (Carpathians, Sudetes, Bohemian Forest and Alps). The cDNA sequences were statistically analysed according to phylogenetical relationships in between specimens collected in separate localities.

Results. During the study, 20 haplotypes were characterized representing a high level of genetic variability, but showing a lack of phylogeographical structure. This pattern can be a result of repeated recolonization and expansion from several areas. Such genetic differentiation may also have been due to the relatively long-term isolation of S. perennis in Pleistocene refugia in Europe, resulting in independent separation of different cpDNA phylogenetic lineages.

Discussion. The lack of phylogeographical structure makes it impossible to indicate the centre of haplotype diversity, but refugia located between the ice sheets in the lowlands, Carpathians, Sudetes or the Alps are the most probable sites, where S. perennis existed in Europe. The lack of evidence for phylogeographic structure possibly indicates a high level of gene flow in the recent. The variation in nucleotide composition of cpDNA may reflect the genetic variability from the ancient period, when the landscape and the fen systems were not fragmented, especially on the lowlands, however, at present, it is difficult to speculate about relations between northern and mountain parts of its distribution range in Europe.