Lepidium

Al-Shehbaz, Ihsan A., 2021, The Afghan Cyphocardamum and Argentinean Lithodraba are united with Lepidium (Brassicaceae), Phytotaxa 516 (1), pp. 111-111 : 111

Lepidium L., Sp. Pl. 2: 643. 1753. Lectotype designated by Green (1925: 317): Lepidium latifolium L.

Britton & Brown (1913: 164) designated the same species a dozen years earlier, but their typification is to be rejected because it followed the American Code (see Turland et al., 2018: Article 10.6).

Cyphocardamum Hedge (1968: 122) , syn. nov. Type:— C. aretioides Hedge (1968: 122) .

Lithodraba Boelcke (1951: 349) , syn. nov. Type:— Lithodraba mendocinensis ( Hauman 1918: 266) Boelcke (1951: 351) .

Lepidium aretioides (Hedge) Al-Shehbaz , comb. nov. Basionym: Cyphocardamum aretioides Hedge (1968:122) . Type:— AFGHANISTAN, Dashti-i-Nawar NW of Ghazni, 3000 m, 8–10 Jun 1965, F. Kasy 28 (holotype, W-1965-0020366!; isotype, E-00039815!).

Lepidium medocinense (Hauman) Al-Shehbaz , comb. nov. Basionym: Xerodraba mendocinensis Hauman (1918: 266) . ≡ Lithodraba mendocinensis ( Hauman 1918: 266) Boelcke (1951: 351) . Type: — ARGENTINA, Mendoza. Valle del Río Tunuyán superior, El Pedernal, 3500 m, 26 March 1918, R. Sanzín s.n. (holotype, BA-3836!). Figure 1 .

Discussion: — Cyphocardamum and Lithodraba resemble Lepidium in having angustiseptate, dehiscent fruits with 1-seeded locules, and they are typically pulvinate, a feature rather rare in Lepidium . However, L. nanum Watson (1871: 30) and L. ostleri Welsh & Goodrich (1980: 80) are narrowly endemic pulvinate species in the western United States ( Al-Shehbaz and Gaskin, 2010). Both genera differ from Lepidium by the scapose habit with few-flowered racemes ( Cyphocardamum ) or solitary flowers ( Lithodraba ), and this “key” difference was used by Appel & Al-Shehbaz (2003) to separate them from Lepidium . However, both L. nanum and L. ostleri are scapose, and this single feature (scapose vs. non-scapose) alone does not justify the recognition of genera in the Brassicaceae . For example, Aphragmus Andrzejowski ex Candolle (1824: 209) has species with well-developed racemes and others with solitary flowers from a basal rosette. Furthermore, most species of Leavenworthia Torrey (1837: 87) produce solitary flowers and/or well-developed racemes on the same plant (see Rollins, 1963). Hedge (1968) considered Cyphocardamum to be closely related to Stroganowia Karelin & Kirilow (1841: 386) , but it is generally agreed that the latter genus is indistinguishable from Lepidium and was united with it nearly two decades ago ( Al-Shehbaz et al., 2002). Although some pulvinate plants in the family produce numerous flowers, none comes even close to those of L. mendocinense in which a single plant may have more than 4,000 flowers ( Figure 1 ). In conclusion, the recognition of Cyphocardamum and Lithodraba as distinct from Lepidium is not supported by molecular data or by a single feature that consistently separates them from the last genus.

Figures

FIGURE 1. Plant of Lepidium mendocinense with 4,217 opened flowers. Photo by Anibal O. Prina.