Thlaspi L.
(excl. Microthlaspi F.K. Mey., Noccaea Moench)
Literature: Clapham (& Akeroyd) (1993), Lambinon & al. (2004), Al-Shehbaz (2010), Stace (2010).
The generic limits of Thlaspi have long been controversial. Meyer (1973) already proposed an alternative generic circumscription and recognized twelve distinct genera, mainly based on seed-coat sculpture and other anatomical characters. Some of these segregates are now confirmed by additional phylogenetic studies (Koch & Al-Shehbaz 2004). In fact, the native genera Microthlaspi and Noccaea are less closely related to Thlaspi s.str. than are the morphologically very different Alliaria Heist. ex Fabr. and Teesdalia R. Brown. Perhaps the latter should also be included in Thlaspi s.str. or Thlaspi further divided as to exclude T. alliaceum. Esmailbegi & al. (2018) indeed propose to transfer T. alliaceum to a newly created genus Mummenhoffia Esmailbegi & Al-Shehbaz (M. alliacea (L.) Esmailbegi & Al-Shehbaz (Esmailbegi & al. 2018).
In its narrow sense Thlaspi only comprises six species from northern temperate regions, including native Thlaspi arvense L. The remainder of the genus in Belgium is transferred as follows:
Thlaspi perfoliatum L. => Microthlaspi perfoliatum (L.) F.K. Mey.
T. montanum L. => Noccaea montana (L.) F.K. Meyer
T. caerulescens J. et C. Presl (incl. subsp. calaminare (Lej.) Dvoráková) => Noccaea caerulescens (J. et C. Presl) F.K. Meyer
For convenience, representatives of the genera Microthlaspi and Noccaea are also included in the key beneath.
1. Annual, without sterile rosettes === 2
1. Biennial or perennial, sterile rosettes always present (native) === Noccaea caerulescens and N. montana
2. Cauline leaves ovate to broadly oblong, cordate-amplexicaul at base. Seeds smooth. Smell of garlic absent when fresh (native) === Microthlaspi perfoliatum
2. Cauline leaves lanceolate to oblong, sessile to slightly amplexicaul-hastate at base. Seeds not smooth. Distinct smell of garlic when fresh === 3
3. Silicula 5-10 mm long, distinctly winged in the upper part only, each loculus with 3-5 seeds. Plant sparsely hairy below === Thlaspi alliaceum
3. Silicula 10-22 mm long, broadly winged throughout, each loculus with 5-8 seeds. Plant entirely glabrous (native) === T. arvense
References
Al-Shehbaz I.A. (2010) Thlaspi. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 745-746.
Clapham A.R. (& Akeroyd J.R.) (1993) Thlaspi. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 1. (2nd ed.). Cambridge University Press, Cambridge: 384-388.
Esmailbegi S., Al-Shehbaz I.A., Pouch M., Mandáková T., Mummenhoff K., Rahimininejad M.R., Mirtadzadini M. & Lysak M.A. (2018) Phylogeny and systematics of the tribe Thlaspideae (Brassicaceae) and the recognition of two new genera. Taxon 67(2): 324-340. [available online at: https://www.researchgate.net/publication/325049044_Phylogeny_and_systema...
Koch M. & Al-Shehbaz I.A. (2004) Taxonomic and phylogenetic evaluation of the American “Thlaspi” species: identity and relationship to the Eurasian genus Noccaea (Brassicaceae). Syst. Bot. 29(2): 375-384.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H.) (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Meyer F.K. (1973) Conspectus der “Thlaspi”-Arten Europas, Afrikas und Vorderasiens. Feddes Repert. 84: 449-470.
Meyer F.K. (1979) Kritische Revision der “Thlaspi”-Arten Europas, Afrikas und Vorderasiens. Feddes Repert. 90: 129-154.
Meyer F.K. (2001) Kritische Revision der “Thlaspi”-Arten Europas, Afrikas und Vorderasiens. Spezieller Teil. 1. Thlaspi L. Haussknechtia 8: 3-42.
Meyer F.K. (2003) Kritische Revision der “Thlaspi”-Arten Europas, Afrikas und Vorderasiens. Spezieller Teil. 3. Microthlaspi F.K. Mey.. Haussknechtia 9: 3-59.
Mummenhoff K. & Zunk K. (1991) Should Thlaspi (Brassicaceae) be split? Preliminary evidence from isoelectric focusing analysis of Rubisco. Taxon 40: 427-439.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.