The naturalized species of Lupinus ( Fabaceae ) in southern Africa

Four species of Lupinus have become naturalized in southern Africa: L. consentinii Guss., L. angustifolius L., L. pilosus Murray and L. luteus L. Their morphological variation and geographical distribution is discussed and a key is provided.


INTRODUCTION
The genus Lupinus comprises some 200 species of annual and perennial herbs, or sometimes subshrubs (Polhill 1976;Bisby 1981).It is best represented in the western parts o f North and South America, with a second centre in Mediterranean Europe with some extensions into the highlands of eastern Africa (Kay 1979).Twelve species of European and African origin are recorded from Africa (Gladstones 1974;Plitmann 1981;W illiams, Demissie & Harbome 1983).
Lupins have been used by man for thousands of years, principally for fodder, green manure, ornament and as grain legumes.A few species have become naturalized weeds in Mediterranean Europe, the south-east United States o f America, the Andes, Australia, New Zealand and South Africa (Kay 1979).
The taxonomy of the genus has been confused for a long time.This was exacerbated to some extent by the development and growing importance of large-seeded lupins as a source of edible protein (Gladstones 1974).The most important grain legumes are Lupinus albus L., L. angustifolius L ., L. luteus L. and L. mutabilis Sweet.
Recent studies on the flavonoid chemistry of the Old World species of Lupinus provide useful taxonomic markers (W illiams et al. 1983) to separate the species cultivated or naturalized in southern Africa.L. albus has flavonols only, L. angustifolius and L. luteus have flavones and flavonols, whereas L. consentinii and L. pilo sus are characterized by the presence of flavone C-glycosides, luteolin and novel 2 'hydroxyflavone.L. angusti foliu s is chemically distinct from all the other Old World species as it accumulates diosmetin derivatives as major leaf constituents (Williams et al. 1983).It is chemically the most variable species and is divided into a number of varieties (Plitmann 1966).
The commercial exploitation o f lupins in South Africa began early this century but it was C .C .P. W agener who first drew attention to the importance of the crop (Van Vuuren 1962).He used bitter lupins as fodder for sheep.Prior to that the crop had been used as a green-manuring crop in vineyards and orchards.By 1947 lupins had be come part of crop rotations in the wheatbelt of the Cape (Preller 1949;Henning 1949).The introduction of sweet lupins at about that time did much to increase wheat yields and resulted in a substantial increase in the number of livestock animals that could be maintained in the region.
Fourteen cultivars were available in 1962 (Van Vuuien 1962): 1, L. albus: albus (German origin), carstens, pflugs gela, pflugs ultra, and S.S.K .(white sweet); 2, L. angustifolius: borre, jackalsfontein, ligvoet, S. E. blue No. 1, B. resistant, blue sweet (German origin) and 7002 (white); 3, L. luteus: S. E. yellow No. 1 and weiko III.The weiko III cultivar is an alkaloid-free, white-seeded and early maturing strain and is the dominant lupin culti vated in a number of European countries.A similar strain named Stellenbosch-Elsenburg Geel-1 is popular in South Africa.Lupins are still popular in the western Cape and have begun to be used in other parts of South Africa, for example, in the south-eastern Transvaal Highveld (Van Zyl 1973).
It was perhaps inevitable that as lupins became increasingly popular some species would become natura lized.This study, based on herbarium material as well as fresh specimens collected during three field trips to the region in 1975, 1976 and 1984, is a first attempt to monitor the spread of naturalized lupins in the Cape.It should be stressed, however, that the distribution maps (Figures 1 -4 ) are only an indication of the extent of naturalization.Botanists, farmers and extension-officers are urged to collect herbarium material from areas which are not recorded in this survey.The author will provide identifications of any well pressed, vouchered material that is sent to him.
Lupinus consentinii is most commonly confused with L. angustifolius but it is easily separated from that spe cies by its much longer, wider, open, oblanceolate leaf lets and obtuse to acute keel petals.Flowering takes place in August and September.
The differences between this species and the only other blue-flowered species, L. consentinii, are given under the former.White-flowered morphs are known to occur in L. angustifolius.It is distinguished from the other three species by the glabrousness of the upper sur face of the leaflets.
Flowering occurs between August and October.This is the most weedy of the naturalized lupins in South Africa.It can eventually form large stands where it has become established.