Psoralea bituminosa

Bituminaria Heist. ex Fabricius (1759: 165) is a small genus of Fabaceae occurring in the Mediterranean (including Black Sea territories) and Canary Islands, currently including four species (Stirton 1981a, 1981b, Boulos 1999, Greuter et al. 1989). Bituminaria was restored by Stirton (1981a), to which he ascribed only two species, previously included in Psoralea Linnaeus (1753: 762), P. bituminosa Linnaeus (1753: 763) [= Bituminaria bituminosa (L.) Stirton (1981a: 318)] and P. acaulis Steven ex Bieberstein (1808: 206) [= Bituminaria acaulis (Steven ex M.Bieb.) Stirton (1981a: 318)]. Afterwards, Greuter (1986) added two more species of Psoralea, P. flaccida Nábělek (1923: 74) and P. morisiana Pignatti & Metlesics (1976: 53) to Bituminaria. Bituminaria bituminosa shows a certain variability mainly in the shape and size of leaves, flowers, pods, as well as the habit and corolla colour (Zohary 1972, Méndez et al. 1991, Jahn & Schönfelder 1995). Such morphological features, that are rather variable within the same population, led to the description of several taxa all referring to this species, e.g. Psoralea palaestina Gouan (1773: 51), P. plumosaReichenbach (1832: 869), P. pontica Khokhrjakov (1997: 52), P. bituminosa subsp. pontica (A.P. Khokhr.) Zernov (2000: 70), P. bituminosa var. brachycarpa Feldmann in Zohary (1972: 455), P. bituminosa var. hulensis Feldmann in Zohary (1972: 455) and P. bituminosa var. prostrata Zohary, (1972: 455), Bituminaria bituminosa var. palaestina (Gouan) R.L. Jahn in Jahn & Schönfelder (1995: 28), B. bituminosa var. albomarginata Méndez et al. (1991: 160) and B. bituminosa var. crassiuscula Méndez et al. (1991: 162). In particular, those varieties described by Zohary (1972) and Méndez et al. (1991) seem to be taxonomically valid, and therefore they could be considered as subspecies of B. bituminosa. However, a proper taxonomic treatment at infra-specific level of this species will require an in-depth analyses in order to verify whether the diacritical characters used for the differentiation of the aforesaid taxa are an expression of the phenotype or are genetically fixed.