Machaerophorus laticarpus Al-Shehbaz, A. Cano, M. Cueva & Salariato, 2018

Al-Shehbaz, Ihsan A., Cano, Asunción, Manchego, Marco Antonio Cueva & Salariato, Diego L., 2018, Remarkable discoveries in the long-neglected and Peruvian-endemic genus Machaerophorus (Brassicaceae), Phytotaxa 360 (2), pp. 114-124 : 118-122

Machaerophorus laticarpus Al-Shehbaz, A. Cano, M. Cueva & Salariato , sp. nov.

Diagnosis:— Macharophorous laticarpus is easily separated from the other two species of the genus by a combination of yellow flowers, lanceolate to oblong-lanceolate fruit 3.5–5 mm wide, and usually obsolete style.

Type:— PERU. Arequipa: Prov. Castilla, Dist. Unión, Anexo Piraucho , entre Sayagrande y Quimbalete. Ladera rocosa empinada, matorral desértico con presencia de cactáceas columnares y arbustos espinosos, 15°40 ʹ 10.5 ʺ S, 72°24 ʹ 50.9 ʺ W, 3258 m, 27 October 2016, M. Cueva 2775 (holotype USM-303015!; isotypes HUSA!, MO-6832092!, MO-6832093!, SI!). Figures 3 , 4 , 5B , 6 .

Description: —Subshrubs, not glaucous, canescent when young, floccose-arachnoid with crisped, flattened, simple and branched trichomes on young parts, puberulent with age. Stems to 1 m tall, woody on lower branches, those of current-year growth herbaceous, erect to ascending, branched, usually densely floccose at and above nodes, becoming puberulent and eventually glabrescent on older parts. Cauline leaves 3–6 cm long, adaxially grooved at least along rachis and petiole; petiole 1.2–4 cm long, floccose at least adaxially within groove, usually sparsely puberulent abaxially; lateral leaf lobes 3–5 on each side, 1–4 cm × 0.5–1 mm, entire, reduced in length upwards; terminal leaf lobe shorter than or about same length as lateral lobes. Racemes 25–56-flowered; rachis puberulent, glabrescent with age; lower and middle fruiting pedicels divaricate-ascending, 10–20 mm long, straight or slightly curved, often secund, usually moderately puberulent at axils, sparsely so elsewhere. Sepals 10–12 mm long, puberulent, yellow-green with yellow margin; petals yellow, 20–23 mm long; blade linear-oblong, 4–6 × 1.5–2 mm, recurved, obtuse to subacute, attenuate to claw 12–14 mm long; filaments yellow, 7–9 mm long; anthers 4–5 mm long; ovules 24–30 per ovary. Fruit lanceolate to oblong-lanceolate or narrowly so, 2.2–3 cm × 3.5–5 mm, not torulose, strongly latiseptate, straight, divaricate or slightly descending, acute at apex, obtuse at base, sessile; valves puberulent, eventually glabrescent; style obsolete or to 0.5 mm long. Seeds biseriate, brown, oblong, apiculate, 1.5–1.8 × 0.8–1 mm.

Distribution: —Endemic to southern Peru and known thus far only from Arequipa department.

Etymology: —The species epithet means broad-fruited, as it has the widest fruit in the genus.

Additional specimens examined (paratypes): — PERU. Arequipa: Prov. Castilla, Dist. Unión, Anexo Piraucho, entre Sayagrande y Dinamarca. Ladera de quebrada, matorral desértico con presencia de cactáceas columnares y arbustos espinosos, 15°40 ʹ 10.3 ʺ S, 72°24 ʹ 29 ʺ W, 3401 m, 27 October 2016, M. Cueva 2770 (HUSA!, MO!, SI!, USM!).

Habitat: — Machaerophorus laticarpus grows in low scruby vegetation and on steep rocky slopes at elevations between 3200 and 3400 m. The main vegetation components of such habitats are the subshrubs Balbisia verticillata Cavanilles (1804: 62) , Tarasa operculata ( Cavanilles 1786: 65) Krapovickas (1954: 134) , Ambrosia artemisioides , Chersodoma jodopappa (Sch. Bip. ex Weddell 1856: 116) Cabrera (1946: 350) , and Ophryosporus peruvianus ( Gmelin 1791: 1269) R.M. King & H. Rob. (1972: 66) , the spiny shrubs such as Adesmia miraflorensis J. Rémy (1846: 357) , Dunalia spinosa ( Meyen 1834: 466) Dammer (1913: 55) , and Proustia berberidifolia ( Cabrera 1953: 48) Ferreyra (1995: 88) , and the columnar cacti such as Corryocactus brevistylus (K. Schum. ex Vaupel) Britton & Rose (1920: 66) , Trichocereus aff. schoenii Rauh & Backeb. in Rauh (1958: 362), and Austrocylindropuntia subulata ( Mühlenpfordt 1846: 347) Backeberg (1939: 12) . According to Zamora (1996) and Leon et al (2006), the habitat of this species corresponds to the Mesoandean Region, which includes the western slopes of the Andes, the inter-Andean valleys and the Altiplano between 2500 and 3500 m.

Discussion: — Machaerophorus laticarpus is easily distinguished from M. matthioloides by having oblong-lanceolate to lanceolate (vs. linear) fruit 2.2–3 cm × 3.5–5 mm (vs. 4–6.2 cm × 2–3 mm) that are acute (vs. acuminate) at apex, obsolete styles rarely to 0.5 mm long (vs. well-developed styles 2–6 mm long), 24–30 (vs. 54–70) ovules/seeds per ovary/fruit, and distinctly biseriate (vs. subbiseriate) seeds. Both species are easily distinguished from M. arequipa by having yellow (vs. white) flowers, strongly flattened (vs. terete) fruit, and biseriate or subbiseriate (vs. uniseriate) seeds.

Machaerophorus matthioloides Schltendal (1845: 469) ; Matthewsia matthioloides (Schltdl.) Müll.Berol. (1868: 144) ; Sisymbrium matthioloides (Schltdl.) Weddell ex E.Fournnier (1965: 144) ; Sibara matthioloides (Schltdl.) Al-Shehbaz (2012a . 17). Described from: “ W. Lechler pl. peruv. Ed. Hohenacker n. 1902, in rupestribus Cordillerae de Tuno Majo m. 1854.” TYPE: Peru, Cordillera de Tuno [Puno], May 1854, W. Lechler 1702 (holotype, HAL-0085367 [image seen]; isotypes, G-00371824!, G-00389254!, GOET-

002935 [image seen], K-000772470!, KW-000127996!, P-00730030!). Figure 5A .

Description: —Herbs suffrutescent? perennial, glaucous, glabresenct. Stems erect to ascending, branched, glabrous throughout or sparsely puberulent at nodes. Cauline leaves 3–6 cm long; petiole 0.5–2 cm long, glabrous or floccose at least adaxially near base; lateral leaf lobes 2–4 on each side, 1–1.5 cm × 0.5–1 mm, glabrescent, entire, gradually reduced upwards in size and number of lateral lobes; terminal leaf lobe about as long as lateral lobes. Racemes 25– 37-flowered; rachis glabrescent; lower and middle fruiting pedicels divaricate-ascending, 12–26 mm long, straight, glabrous. Sepals 14–16 mm long, glabrous, margin membranous; petals yellow, linear to linear-oblanceolate, 21–27 mm long, blade 6–9 × 1.5–2 mm, obtuse; claw 15–17 mm long; filaments 12–16 mm long; anthers 4–6 mm long; ovules 54–70 per ovary. Fruit linear, 4–6.2 cm × 2–3 mm, latiseptate, straight or slightly curved; valves glabrous, base obtuse, apex acuminate; style 2–6 mm long. Seeds subbiseriate, brown, ovate-oblong, compressed, margined, 1.2–1.6 × 0.7–1.1 mm.

Distribution: —Endemic to southwestern Peru but exact location unknown.

Etymology: —The species epithet is derived from the generic name Matthiola Aiton (1812: 119) due to similarities in aspects of fruit and flowers.

Discussion: — Machaerophorus matthioloides most closely resembles M. laticarpus , especially in having latiseptate, non-torulose fruit and yellow flowers, and they are readily separated from each other by characters listed under the latter species. Because the basal parts of M. matthioloides are missing, it is not possible to determine if the species is a subshrub or suffrutescent herb.

Figures

FIGURE 3. Machaerophorus laticarpus. A. Plant. B. Flower. C. Petal. D. Stamen. E. Fruit and fruiting pedicel. Drawn by Al-Shehbaz from isotype (MO 6832092).

FIGURE 4. Machaerophorus laticarpus. A. Plants. B. Portion of inflorescence. C. Branch. D. Infructescence showing second fruit. Photos by M. Cueva.

FIGURE 5. Fruit of Machaerophorus. A. M. mathioloides. B. M. laticarpus. C. M. arequipa. Drawn by Al-Shehbaz. A from isotype (P 00730030), B from isotype (MO 6832092), C from paratype (MO 6701113).

FIGURE 6. Distribution map of Machaerophorus arequipa (circle) and M. laticarpus (triangle).