Lepidium weigendii Al-Shehbaz, 2023

Lepidium weigendii Al-Shehbaz View in CoL , sp. nov.

Diagnosis:— Lepidium weigendii is easily distinguished from the related L. crassius by having densely hirsute and notched (vs. glabrous and notchless) fruits, persistent (vs. caducous) nectar glands, and petals differentiated (vs. undifferentiated) into blade and claw.

Type:— PERU. Dept. Arequipa: Prov. Caravei, Lomas ca. 3 km E of km 655 of Panamericana Sur , 350–960 m, sandy and rocky places, 4 October 1997, M. Weigend & H. Förther 97/738. Holotype, MSB; isotype, USM (n.v.) . Figures 1 View FIGURE 1 , 2 View FIGURE 2 .

Description:— Herbs, annual, densely hirsute. Trichomes spreading, straight, 0.1–0.6 mm long. Stems ca. 30 cm tall, erect, branched below middle and above, densely hirsute. Basal leaves fall off early; middle cauline leaves oblong to oblongovate or elliptic, 1.5–4 × 0.5–2 cm, sessile, hirsute, base auriculate, margin serrate, with 3–6 teeth on each side, apex acute. Racemes lax, elongated considerably in fruit; rachis straight, densely hirsute with straight trichomes to 0.6 mm long; fruiting pedicels slender, straight, divaricate-ascending, 5–10 mm long, densely hirsute all around, terete, not winged or margined, 0.25–0.33 mm wide. Sepals oblong, 1.5–1.7 mm long, caducous, margin and apex white, puberulent outside; petals white, obovate, 2–2.5 × 1–1.2 mm, base attenuate, apex rounded; claw 0.5–1 mm long; stamens 4, 2 median and 2 lateral; filaments 1.2–2 mm long; anthers oblong, 0.5–0.6 mm long; nectar glands 4, conical, 0.4–0.7 mm long, alternating with filament bases, becoming spreading and persistent well after fruit maturity; ovules 2 per ovary. Fruits dehiscent, orbicular to suborbicular, 4.5–6 × 4.5–5 mm, strongly angustiseptate, not inflated; valves papery, veinless, densely hirsute with spreading trichomes, smooth, strongly keeled, wingless; apical notch 0.2–0.4 mm deep; septum complete; style 0.5–1 mm long, exserted above fruit notch; stigma entire. Seeds reddish brown, ovate, wingless, 2.5–3 × 1.2–1.5 mm; cotyledons incumbent, entire.

Eponymy: —The species is named after one of its collectors, Maximilian Weigend ( 25 September 1968 –), director of the Bonn Botanic Garden, Systematic Botany, and Herbarium.

Habitat: —Sandy and rocky areas; 350–960 m.

Distribution: —Endemic to southern Peru.

Taxonomic notes: — Lepidium weigendii is known thus far only from the type locality. It is most closely related to L. crassius , another South Peruvian endemic to Dept. Arequipa. From the latter, the novelty is easily distinguished by having densely hirsute (vs. glabrous) fruits 4.5–6 × 4.5–5 mm (vs. 3–4.5 × 3–4.5 mm), well-developed (vs. lacking) apical notch, clawed (vs. clawless) petals, and conical nectar glands that persist (vs. fall off) well after (vs. before) fruit maturity.

Lepidium weigendii is unique among all of the 55 native South American congeners by the presence of densely hirsute (vs. glabrous or at most puberulent) fruits. Of the nine Lepidium species on that continent that have puberulent fruits, L. arequipa Al-Shehbaz (2017: 403) , L. beckii Al-Shehbaz (1999: 5) , and L. ecuadoriense Thellung (1906: 222) are puberulent on the entire valves, though the last may be so only when the fruits are young. In L. argentinum Thellung (1928: 9) , L. boelckei Al-Shehbaz (1989: 1189) , and L. strictum ( Watson 1876: 46) Rattan (1888: 25) the fruits are either glabrous or puberulent. Finally, only the valve keel is minutely puberulent in L. pubescens Desvaux (1815: 180) , L. rahmeri Philippi (1891: 5) , and L. stephan-beckii Al-Shehbaz (2017: 412) . In addition, L. weigendii differs from all these by its persistent (vs. caducous) nectar glands at the fruit base.

Lepidium weigendii may be confused with the Peruvian endemic L. cyclocarpum , which is also hirsute annual with orbicular, notched fruits, but it differs by the auriculate cauline leaves, four stamens, clawed petals, hirsute, non-reticulate fruits 4.5–6 × 4.5–5 mm, and persistent nectar glands. By contrast, L. cyclocarpum has non-auriculate cauline leaves, only two median stamens, non-clawed petals, glabrous, reticulate fruits 3.5–4 × 3–3.8 mm, and caducous nectar glands.

The Chilean-endemic Lepidium spathulatum Philippi (1860: 8) is a third species with orbicular fruits and hirsute stems that might also be confused with L. weigendii . However, it differs from the present novelty by being a perennial (vs. annual), with exauriculate (vs. auriculate) cauline leaves, adaxially puberulent and abaxially glabrous fruiting pedicels (vs. densely hirsute all around), petals undifferentiated (vs. differentiated) into blade and claw, two median (vs. two lateral and two median) stamens, and glabrous (vs. densely hirsute) fruits