Descurainia pinnata (Walter) Britton (N-Am.) – A very rare and ephemeral alien. Formerly recorded once as a wool alien in the valley of river Vesdre near Verviers (1894). In 2011 seen by a roadside in the port of Gent near a grain storage. Alien records of Descurainia pinnata are rather scarce in Europe. Clement & Foster (1994) provide some wool alien records from the British Isles.
Descurainia pinnata is the most widespread and variable species in North America. It includes several overlapping and intergrading subspecies. Recent molecular studies have demonstrated that Descurainia pinnata is not a monophyletic species and consists of at least two distinct lineages (Goodson & al. 2011). The record from Gent seems to belong with subsp. brachycarpa (Richardson) Detling. The taxonomic position of this subspecies remains unresolved; it is closest to Descurainia pinnata s.str. but might be a distinct species (Goodson & al. 2011).
References
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Goodson B.E., Rehman S.K. & Jansen R.K. (2011) Molecular systematics and biogeography of Descurainia (Brassicaceae) based on nuclear ITS and non-coding chloroplast DNA. Syst. Bot. 36(4): 957-980.