SRA

Krascheninnikovia ceratoides (L.) Gueldenst. (Chenopodiaceae) is a steppe plant with two subspecies, K. ceratoides subsp. ceratoides, which is widespread in the Eurasian steppe, and K. ceratoides subsp. lanata, which grows in the intermountain region of western North America. Krascheninnikovia ceratoides is characteristic of the Eurasian steppe, and a few disjunct populations can also be found in Austria (on loess) and Spain (on soils rich in gypsum and nitrogen). To understand the history and development of the Eurasian steppe, we investigated differences at the DNA level, which can reflect the phylogeographic history of this species. To this aim, we sequenced several loci including ITS and ETS to reconstruct infraspecific relations. Furthermore, we identified the level of ploidy of the individuals. While diploid, triploid, tetraploid and hexaploid individuals have been reported in the literature, we were only able to find diploid and tetraploid individuals. The diploids were found in the east of Mongolia, Kazakhstan, Kyrgyzstan, Russia and the USA. The tetraploids were located in the west of Mongolia, Kazakhstan, Tajikistan, Russia, and Europe. The populations were uniformly di- or tetraploid. Our results indicate that the species may have spread from the Mongolian Altai Mountains in two opposite directions – on the one hand at the diploid level to the east, to East Asia and North America, and on the other hand at the diploid and tetraploid level to the west, to Central Asia and Europe. The European disjunct populations are tetraploid. Fossil-calibrated gene trees were also used to estimate the age of the species. It is probably of Middle or Late Miocene age, and the first split among extant lineages of the species took place over 2 million years ago. The spread of the main lineages found in Central and East Asia could be related to major phases of steppe expansion.