Microthlaspi erraticum (Jord.) T. Ali et Thines has a wide distribution, ranging from the Alps to the Tien Shan

- Microthlaspi erraticum and M. perfoliatum are confirmed as distinct species.
- Two distinct subclades of M. perfoliatum s.l. are from Western Europe.
- A third distinct subclade is found throughout the entire range.
- Microthlaspi erraticum is more homogenous, most divergent clades from the Balkans.
- Microthlaspi erraticum is not restricted to central Europe but ranges from there to the Tien Shan.

Microthlaspi is a predominantly Eurasian genus which also occurs in the northernmost parts of Africa (Maghreb). The most widespread species of the genus is M. perfoliatum, which can be found from Sweden to Algeria and from Portugal to China. The other species are thought to have much more confined distribution ranges, often covering only a few hundred kilometres. This is also believed for the diploid M. erraticum, which was recently re-appraised as a taxon independent from the tetra- to hexaploid M. perfoliatum. Previously, M. erraticum was believed to be present only in Central Europe, from the East of France to Slovenia. In order to gain a deeper understanding of the ecology, evolution and migration history of Microthlaspi it was the focus of the current study to investigate, if M. erraticum is present in habitats outside Central Europe, but with microclimates similar to Central Europe. It is demonstrated that M. erraticum is much more widespread than previously thought, while other lineages apart from M. perfoliatum s.str. and M. erraticum seem to have restricted distribution ranges. The latter species was observed from the Alps and their foreland, the Balkans, the mountainous areas around the Black Sea, Southern Siberia, as well as the Altai and Tien Shan mountains. This demonstrates a widespread occurrence of this easily-overlooked species.