Ruscus L.
The systematic position of Ruscaceae long remained unclear (e.g. Jang & Pfosser 2002). It was often included in Liliaceae and was still treated as such in the Belgian flora (Lambinon & Verloove 2012). However, molecular phylogenetic research supports the segregation of Ruscaceae from Liliaceae. According to Chase (2004) Ruscaceae is probably better included in a broadly circumscribed Asparagaceae which is in accordance with molecular data (APGIII 2009). This classification was followed in most contemporary floras in western Europe (e.g. Stace 2010, Tison & de Foucault 2014).
Ruscus is a small Old World genus of six species (Mabberley 2008). All are native from the Azores to western Asia but none is native in Belgium. The genus is fairly popular in horticulture. At least five species and a hybrid are cultivated as ornamentals (e.g. Yeo 1986, Jäger & al. 2008). One of these, Ruscus aculeatus, has been recorded as an escape from or relic of cultivation in Belgium. An additional species, R. hypoglossum L., from southeastern Europe and Turkey, is known to be locally naturalized in the British Isles (Clement & Foster 1994) and was discovered in 2008 in coastal dunes in Bray-Dunes (France), close to the Belgian frontiers. It is usually smaller (up to 40 cm tall) with an unbranched stem and spineless cladodes.
Interesting additional information on Ruscus (incl. keys to the species) is provided by the Plant Heritage Devon Group at: http://www.plantheritagedevon.org.uk/collections/item/88-ruscus-articles
Literature:
APG III (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. APG III. Bot. J. Linn. Soc. 161(2): 105-121. [available online at: http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.2009.00996.x/full]
Arber A. (1924) Danae, Ruscus and Semele: a morphological study. Annals of Botany 38: 229-260.
Chase M.W. (2004) Monocot relationships: an overview. Amer. J. Bot. 91(10): 1645-1655. [available online at: http://www.botany.wisc.edu/courses/botany_940/05Frontiers/papers/13Chase.pdf]
Chase M.W., Reveal J.L. & Fay M.F. (2009) A subfamilial classification for the expanded asparagalean families Amaryllidaceae, Asparagaceae and Xanthorrhoeaceae. Botanical Journal of the Linnean Society 161(2): 132-136.
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Jang C.G. & Pfosser M. (2002) Die Phylogenie der Ruscaceae sensu lato - analysiert mit Hilfe von rbcL and trnL-F DNA-Sequenzen. Stapfia 80: 333-348. [available online at: http://www.zobodat.at/pdf/STAPFIA_0080_0333-0348.pdf]
Khokhrjakov A.P. & Tichomirov V.N. (1993) On a new genus Platyruscus A. Khokh. et V.N. Tichom. (in Russian). Byull. Mosk. Obshch. Ispyt. Prir., Biol. 98(4): 91-93.
Kim J.-H., Kim D.-K., Forest F., Fay M.F. & Chase M.W. (2010) Molecular phylogenetics of Ruscaceae sensu lato and related families (Asparagales) based on plastid and nuclear DNA sequences. Amer. J. Bot. 106(5): 775-790. [available online at: http://aob.oxfordjournals.org/content/106/5/775.full]
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Tison J.-M. & de Foucault B. (coord.) 2014) Flora Gallica. Flore de France. Editions Biotope, Mèze : xx + 1196 p.
Yeo P.F. (1964) A contribution to the taxonomy of the genus Ruscus. Notes Roy. Bot. Gard. Edinburgh 28: 237-264.
Yeo P.F. (1986) Ruscus. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1: 265-266. Cambridge University Press, Cambridge.