Rumex fueginus Phil. (syn.: Rumex maritimus L. subsp. fueginus (Phil.) Hultén, R. maritimus var. fueginus (Phil.) Dusén) (Am.) – An exceptional but possibly overlooked alien. Discovered in 2011 on sand raised sites in the port area of Zeebrugge. Confirmed in this area in 2012 in three or four distinct localities (all in different IFBL squares) and possibly more or less established. In 1893 also recorded as an ephemeral wool alien in the valley of river Vesdre near Verviers.
Records of Rumex fueginus seem to be rare in Europe, except in Scandinavia (Jørgensen 1971, Karlsson 2000). In the British Isles it was formerly recorded as a wool alien (Rechinger 1948, Lousley & Kent 1981). In Scandinavia (Denmark, Finland, Norway, Sweden) it is known since the 19th century but usually remains ephemeral. However, in Denmark Rumex fueginus seems more stable on sandy sea shores. There it seems to intergrade with native Rumex maritimus (Karlsson l.c.). For that reasons it is accepted as a subspecies of the latter in Flora Nordica.
A partial revision of Belgian specimens of Rumex maritimus aggregate confirms that R. fueginus and R. maritimus are closely related but distinct. Specimens that combine all the features of Rumex fueginus (see key) have only been seen from the Vesdre valley (19th century) and Zeebrugge (extant populations). Rechinger (1937), who was familiar with Eurasian rumices, distinguished Rumex fueginus (and other American representatives of this aggregate) by the presence of minute rough papillae on stems and leaves and stated that these were completely absent in Eurasian R. maritimus. However, vegetative parts of the latter may also display some papillose pubescence (as seen in BR). This is rather surprising: either Rechinger was incorrect or both species, once geographically isolated, intergrade since they occur sympatrically in parts of Europe. Additional research seems necessary. For the time being and given their straightforward distinction in Belgium, both are tentatively accepted as good species in the present account.
Finally, other species of the Rumex maritimus aggregate might have been overlooked. In Scandinavia (Karlsson 2000) at least two additional species have been recorded: Rumex marschallianus Reichenb. and R. trisetifer Stokes, both with a predominantly Asian distribution. These species are distinguished mainly by valve characters (number of teeth per side, number of tubercles, etc.) (see Rechinger 1949). Records of Rumex maritimus in highly artificial places (unloading quays in port areas, etc.) therefore might hide non-native look-alikes and should be critically assessed.
For additional information on the discovery of this species in Belgium see also here: http://alienplantsbelgium.be/content/rumex-fueginus-0.
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Selected literature:
Jørgensen P.M. (1971) Rumex maritimus L. og R. palustris Sm. i Norge. Blyttia 29(3): 133-139.
Karlsson T. (2000) Polygonaceae. In: Jonsell B. (ed.), Flora Nordica, vol. 1. The Bergius Foundation, Stockholm: 235-318.
Lousley J.E. & Kent D.H. (1981) Docks and knotweeds of the British Isles (BSBI Handbook n° 3). BSBI, London: 205 p.
Mosyakin S.L. (2005) Rumex. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 5. Oxford University Press, New York-Oxford: 489-533.
Rechinger K.H. (1937) The North American species of Rumex. (Vorarbeiten zu einer Monographie der Gattung Rumex 5.) Publ. Field Mus. Nat. Hist., Bot. Ser. 17: 1-150.
Rechinger K.H. (1948) Beiträge zur Kenntnis von Rumex, IX. Candollea 11: 229-241.
Rechinger K.H. (1949) Rumices Asiatici. (Vorarbeiten zu einer Monographie der Gattung Rumex 7.) Candollea 12: 9-152.