Arabis alpina L. subsp. caucasica

Arabis alpina L. subsp. caucasica (Willd. ex Schlecht.) Briq. (syn.: A. caucasica Willd. ex Schlecht., A. albida Steven) (S-Eur., SW-As.) – A rather rare but increasing, locally naturalized escape from cultivation. First recorded (without further details) in Fosses in 1881. Subsequently observed in rather numerous, very widely scattered locations but more frequently in Wallonia. Recently confirmed to be naturalized from Cugnon (Thoen 1999), Pepinster (1983), Kortrijk (2004), Tournai (cemetery), etc. Perhaps often overlooked or merely neglected by botanists.

Arabis alpina subsp. caucasica preferably grows on old sun-exposed walls (more rarely on calcareous rocks near habitations). Records in other habitats (foot of walls, cracks in pavement, dumps, etc.) are usually ephemeral.

Most Belgian populations obviously belong to typical Arabis alpina subsp. caucasica: large petals (often more than 10 mm long), more densely white canescent leaves with distinctly stalked basal leaves, longer siliqua, etc. This is the usual garden plant in Europe (Akeroyd 1995), although the contrary is true in North America (Al-Shehbaz 2010). However, some populations are somehow reminiscent of genuine Arabis alpina (s.str.) or are more or less intermediate. A population from an old wall in Landelies for instance has stalkless basal leaves but otherwise corresponds with subsp. caucasica.  Both subspecies probably only represent the extremes of one variable species and are possibly better treated as conspecific. However, recent molecular studies demonstrated that Arabis alpina is a paraphyletic species (Karl & al. 2012).

Arabis alpina subsp. caucasica, Yvoir, old wall, April 2012, P. Vanmeerbeeck Arabis alpina subsp. caucasica, Yvoir, old wall, April 2012, P. Vanmeerbeeck
Arabis alpina subsp. caucasica, Yvoir, old wall, April 2012, P. Vanmeerbeeck  

Selected literature:

Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.

Al-Shehbaz I.A. (2010) Arabis. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 257-266.

Gottschlich G. & Raabe U. (1988) Arabis alpina L., Hieracium schmidtii Tausch und Hieracium onosmoides Fr. an den Bruchhauser Steinen, Hochsauerlandkreis. Floristische Rundbriefe 22: 10-13.

Karl R., Kiefer C., Ansell S.W. & Koch M.A. (2012) Systematics and evolution of arctic-alpine Arabis alpina (Brassicaceae) and its closest relatives in the eastern Mediterranean. Am. J. Bot. 99(4): 778-794.

Kirchner D.E. (2002) Phylo-Geographie von Arabis alpina L. (Brassicaceae). Bot. Jahrb. 124(2): 183-210.

Koch M.A., Kiefer C., Ehrich D., Vogel J., Brochmann C. & Mummenhoff K. (2006) Three times out of Asia Minor: the phylogeography of Arabis alpina L. (Brassicaceae). Molec. Ecol. 15(3): 825-839.

Thoen D. (1999) La flore du bassin hydrographique de la Semois. Observations chorologiques et écologiques sur la période 1995-1997. Adoxa 22: 11-20.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith