Presliophytum heucheraefolium (Killip) Weigend (2006: 467)

Acuña, Rafael & Weigend, Maximilian, 2017, A taxonomic revision of the western South American genus Presliophytum (Loasaceae), Phytotaxa 329 (1), pp. 51-68 : 60-61

2. Presliophytum heucheraefolium (Killip) Weigend (2006: 467) ( Figs. 1E , 2C, D , 3B, H, J)

≡ Loasa heucheraefolia Killip (1928: 90)

Type: — PERU [Áncash, Prov.Huaraz], Tambo de Pariacota [sic], ca. 1000 m., moist cliff, 8 October 1922, F.Macbride & [ W.] Featherstone 2543 (holotype: F No. 518960/ Neg. No. 63414! [photo: US barcode US 00115211!]; isotype: G barcode G00368197 [photo!]) .

Coarse, densely branched perennial shrub 50–150 cm tall. Stem epidermis with abundant glochidiate, short-smooth and glandular trichomes, sparse scabrid and stinging trichomes. Taproot present, usually thickened and fleshy. Leaves lobate, opposite below, alternate above, petiole 20–100 mm, with glochidiate, short-smooth, glandular and scattered stinging trichomes, lamina 25–170 × 30–170 mm, reniform, with 3–8 lobes on each side, margin crenate, base deeply cordate, blade and lobe apices obtuse, upper side with numerous short-smooth, glandular and few stinging trichomes, very rarely with scabrid trichomes, underside with glochidiate, scabrid and glandular trichomes (rarely with stinging trichomes on veins). Inflorescences densely frondose, complex asymmetrical dichasia, to ca. 100 cm long; each flower erect or horizontal in anthesis, with two, often sessile, prophylls (flowers apparently solitary and irregularly alternating with foliage leaves) 20–60 × 20–65 mm, similar to vegetative leaves in morphology and indumentum; pedicels with glochidiate, scabrid, glandular, short-smooth and scattered stinging trichomes. Sepals five, lanceolate, 10–12 × 3–5 mm green, 3-veined, with entire margins, at least twice as long as wide, indumentum of each surface similar to that of the respective leaf surface; petals five, full spreading, cymbiform, 17–25 mm long, white to lightly tinged greenish, darker greenish on the abaxial surface, with glochidiate, scabrid, short-smooth, glandular and scattered, weak stinging trichomes, margins entire to wavy; nectar scales five, 5–7 mm long, white (not contrasting with petal color), unicolored, concave, slightly bulging, with a poorly developed papillae-margined neck and rudimentary apical wings. Filiform dorsal threads, three, 5–7 mm long, all of about the same length, attached subapically to the scale. Staminodes 2 per scale, 15 mm long, sigmoid, distal 2/3rds filiform and glabrous, proximal third abruptly expanded, with a flange towards the scale, margins papillose. Stamens 100–150, filaments 10–15 mm long. Style 10–15 mm long, straight, but twisting after fertilization, ovary inferior, with a densely pubescent roof, with abundant short-smooth trichomes, outer wall with abundant glochidiate, short-smooth, glandular and stinging trichomes, placentae 3–5. Fruit a capsule 10–12 mm diameter, obovoid to subglobose, opening with 3–5 apical valves; seeds ca. 2000–5000 per capsule, 0.5 mm × 0.2–0.5 mm, testa dark brown, foveate-reticulate. Seed testa cells polygonal.

Notes:— Killip (1928) considered this species to be closely related to Loasa pallida , but this is not correct (see Acuña et al. 2017). The species is very distinctive due to its reniform leaves with a densely glandular indumentum.

Etymology:— The epithet refers to the similarities in leaf shape between this species and Heuchera L. ( Saxifragaceae ).

Illustrations:— Floral diagram: Grau (1997: Ab. 1). Sepal morphology: Weigend (1997: Fig. 40.1).

Distribution:— Endemic to Peru. Restricted to Departamento de Áncash and the northern part of Departamento de Lima from 400 to 1200 m ( Fig. 4 ). Mainly on the western slope of the Cordillera Negra.

Phenology:— In the wild this species is known to flower in April, May, October and November. In cultivation it flowers all year.

Ecology:— Presliophytum heucheraefolium grows on cliffs, dry washes, road banks and scree slopes at low to intermediate elevations, sometimes associated with other xeric habitat plants such as cacti and Tiquilia Persoon (1805: 157) . Thigmonastic stamen movements were studied by Henning & Weigend (2012).

Conservation status:— This species seems to be rare in nature and because of that, relatively poorly collected. It was considered as endangered (EN), B1ab(iii) by Rodríguez and Weigend (2006).

Additional specimens examined:— PERU. Áncash: Prov. Santa, 49 Km above Santa in Río Santa Valley , 400 m, 13 May 2003, Weigend et al. 7653 ( BONN, F) ; Road from Moro to Pamparomas ( Caraz ), Cordillera Negra , 900 m, 1997, Weigend & Dostert 97/120 ( F, P) ; Road from Moro to Pamparomas.Arenal de Moro , 615 m, 25 November 2006, Ackermann & Albán 615 ( BONN) ; Road from Moro to Pamparomas , 10 October 2002, Weigend et al. 7368 ( BONN) ; Prov. Casma, Road from Casma to Yaután , 580 m, 10 April 2001, Weigend et al. 5536 ( BONN) ; Prov. Huaraz, Río Grande / Río Cacchan , 1141 m, 16 May 2003, Weigend et al. 7691 ( BONN, F) .

Figures

FIGURE 1. Vegetative morphology of Presliophytum.A. Habit andhabitat of shrubby Presliophytum incanum (Quinistaquillas, Moquegua, Peru, not vouchered). The three species of Peruvian Presliophytum have similar habits. B. Habit and habitat of subshrubby Presliophytum sessiliflorum (Quebrada La Chimba,Antofagasta, Chile, Luebert et al. 3405, BONN; photo courtesy of F. Luebert).C. Habit and habitat of herbaceous Presliophytum malesherbioides (Juntas del Toro, Coquimbo, Chile, not vouchered; photo courtesy of M. Eyzaguirre). Mature specimens of this species range from unbranched annuals to densely branched subperennial herbs as the one illustrated. D. Mature leaf of Presliophytum arequipense (cultivated, seeds collected near Mollendo, Arequipa, Peru, Ortiz et al. 121, BONN). E. Mature leaf of Presliophytum heucheraefolium, (cultivated, seeds collected near Río Cacchán, Áncash, Peru, Weigend et al. 7691C, BONN). F. Mature leaf of Presliophytum incanum (cultivated, seeds collected near Ullpan, Áncash, Peru, Weigend & Hilger 8912C, BONN). G. Mature leaf of Presliophytum incanum (cultivated, seeds collected near Omate, Moquegua, Peru, Ackermann & Cáceres 674, BONN). Scale bars 15 mm. Photos by R.Acuña and M. Weigend, unless otherwise credited.

FIGURE 2. Microstructure and trichome morphology of Presliophytum. A. Adaxial foliar surface of a mature leaf of Presliophytum arequipense (Ortiz et al. 121, BONN). Presliophytum incanum has virtually identical indumentum. B. Abaxial foliar surface of a mature leaf of Presliophytum arequipense (Ortiz et al. 121, BONN). Presliophytum incanum may have similar indumentum or mostly made up by scabrid trichomes. C. Adaxial foliar surface of a mature leaf of Presliophytum heucheraefolium (Weigend et al. 7691C, BONN). This species and Presliophytum sessiliflorum have abundant and relatively long uniseriate glandular hairs, on leaves and younger stems. Presliophytum malesherbioides has similar but much shorter trichomes in some areas of the stem. D. Abaxial foliar surface of a mature leaf of Presliophytum heucheraefolium (Weigend et al. 7691C, BONN). GL: Glochidiate trichome, GT: Uniseriate glandular trichome, SC: Scabrid trichome, SS: Short smooth trichome. Scale bars A, B: 100 μm; C, D 200 μm.

FIGURE 4. Natural distribution of Presliophytum based on herbarium specimens. P. incanum W = Presliophytum incanum with white or indeterminate color corollas. P. incanum Y = Presliophytum incanum with yellow corollas.