Platycarpum loretensis Dávila & L. Kinoshita, 2016

Dávila, Nállarett & Kinoshita, Luiza Sumiko, 2016, A new species of Platycarpum (Rubiaceae, Henriquezieae) from Peruvian Amazon, Phytotaxa 260 (3), pp. 276-282 : 277-281

Platycarpum loretensis Dávila & L. Kinoshita sp. nov., Figs. 1 , 2 , 3

Type:— PERU. Loreto: Requena, Jenaro Herrera , Quebrada Sapuena , 13 Sep 1989 (fl, fr), Freitas s/n.TB-Cha P 1-II-10 (holotype, AMAZ! ; isotypes, F! , MO! ).

Diagnosis:This new species is similar to Platycarpum orinocense in having opposite leaves,brownish-hirsute pubescence on the abaxial side of the leaves, inflorescences and stipules; the former differs from the latter by its oblanceolate leaf blades (vs. elliptic to ovate to broadly obovate in P. orinocense ) with intersecondary veins prominulous below (vs. without intersecondary veins), corollas 1.9–3 cm long (vs. 1.2–2(–2.2) cm long), and fruits 4.7–5.5 × 3.6–4.9 cm (vs. 3–3.5 × 2.8–3.5 cm), and by being endemic to Peru (vs. distributed in Colombia and Venezuela).

Trees 15–30 m tall, 10–40 cm dbh; outer bark fissured, with red exudate when cut ( Fig. 3C ). Young stems terete between nodes, laterally compressed near the nodes, sometimes with sparse lenticels, pubescence in two layers, shorter layer sparsely strigose with trichomes whitish or translucent, 0.1–0.2 mm long, longer layer densely hirsute with trichomes ferruginous, 1.4 mm long. Stipules interpetiolar, lanceolate, 2.7–3.1 cm long, caducous, adaxially densely creamy villous, abaxially densely ferrugineous hirsute, with trichomes 0.6 mm long. Leaves opposite; petioles (0.7) 1.8–2.9 cm long, with pubescence in two layers, shorter layer sparsely strigose-whitish, longer layer hirsute-ferruginous, with one gland near abaxial base, inverted U-shaped to slightly rectangular, 0.3–0.4 cm long, dark when dry; blades oblanceolate, (13)16.3–30 × 5.4–10 cm, cuneate at base, acute to rounded at apex, with venation brochidodromous; secondary veins (15)17–19 on each side of midrib, adaxially strigose, abaxially papillose with cinereous wax, tomentose-ferruginous, midrib and secondary veins with ferruginous hirsute and antrorse indument (trichomes 1–1.2 mm), intersecondary veins conspicuous and prominulous, tertiary veins prominulous. Inflorescences cymose, 20–23.7 cm long, secondary branches two per node, with 4–5 orders of branching; bracts foliaceous at first and second basal nodes, 5 × 0.3 cm, bracts subtending distal axes linear, 0.7–1.2 cm long, pubescent in two layers, with longer layer hirsute-ferruginous, shorter layer tomentose-yellowish. Flowers pedicellate, pedicels 0.4–1 cm long; hypanthium obconic, 0.2–0.3 cm long, ferruginous-tomentose. Calyx lobes 4–5, elliptic to oblong, 1–1.1 × 0.4–0.6 cm, externally with pubescence in two layers, shorter layer villous, longer layer sparsely tomentose, internally yellowishsericeous. Corolla funnelform, 1.9–3 cm long, externally pale yellow, pubescence in two layers, shorter layer villous, longer layer tomentose, internally white with red maculae in the throat, puberulous, with a ring of trichomes at base, one lobe bearded, yellow; lobes 5, elliptic, 0.7–1.2 cm long, acute, with undulated margins. Stamens 5, inserted at two different heights in corolla tube; filaments 5–8 mm long; anthers 0.3–0.4 cm long, cordate at base, acute at apex. Pollen grain spherical, 4-colp(oroid)ate, 45–49 μm in diameter at equator, sexine reticulate. Disk tomentose at apex; style 1–1.2 cm long, stigmatic lobes 2, 0.1 cm long. Fruits capsular, elliptic in outline, markedly flattened 4.7–5.5 × 3.6–4.9 cm, verrucose and tomentose-ferruginous, loculicidal dehiscent. Seeds elliptic, 4.9 × 2.1 cm, hilar margin straight, with surface pitted, with remaining portion narrowed into marginal wing 0.3 cm wide.

Discussion

Platycarpum loretensis can be identified by its oblanceolate leaves with adaxial side strigose, and abaxial side with conspicuous, prominulous intersecondary veins, papillose, covered by gray wax, and a tomentose-ferruginous indument ( Fig.2 B–C ) with a grayish-reddish appearance; cymose inflorescences 20–23.7 cm long with 4–5 orders of branching; corollas 1.9–3 cm long, and fruits ovate-retuse in outline, 4.7–5.5 × 3.6–4.9 cm.

As several other species of the genus, Platycarpum loretensis is found in forests on dry to inundated white sand substrates and local wetlands (i.e., peatlands and palm swamps) in the western Amazon basin of Peru, which represents the western limit of the generic distribution. This species appears to be locally abundant, although not widely distributed in the Department of Loreto ( Fig. 4 ). Quantitative inventories in seven areas of white-sand forests by Fine et al. (2010) showed that it is among the ten most abundant species in transects of 0.5 ha established in the localities of Tamishiyacu and Jenaro Herrera (identified as P. orinocense ). Likewise, Freitas (1996), in an intensive sampling of different types of vegetation in Jenaro Herrera, recorded P. loretensis (named as Platycarpum JH-SP 1) in white-sand, upland forests and swamp forests. Valderrama (2013) sampled areas identified as peatlands in San Jorge (Tamshiyacu, Loreto), which are oligotrophic areas with large accumulations of organic material from decomposing plants (Lätheenoja et al. 2009), and found P. loretensis to be among the most abundant species in 0.5 ha transects (24–172/356–513 individual/total individuals transects).

Distribution and ecology: This species is found in forests on white-sand substrates, both upland and, swamp forests, and also in peatlands, at ca. 110 m elevation in the western Amazon basin, Loreto Department, Peru.

Conservation status: This species is classified as Least Concern (LC) according to the IUICN (2014) categories, because is recorded in three localities, and in each locality the species is locally abundant. Nevertheless, none of the locality of occurrence of this species belongs to a conservation area.

Phenology: Flowers were collected in September; fruits were collected in September, November, and January.

Etymology: The specific epithet refers to the Peruvian department where the species was first collected.

Additional specimens examined (paratypes): PERU. Loreto: Maynas, Dtto. Fernando Lores, Río Amazonas , Isla de Aguajal , aprox. 2 horas de Tamshiyacu, 6 September 1988, M. Rimachi 8767 ( MO, NY, UMS) ; vicinity of Iquitos, 1977, J. Revilla 4287 ( MO) ; Requena, Dtto. Sapuena, Basin of Rio Ucayali, Jenaro Herrera and vicinity, 4º 55’ S, 73 º 45’W, at 5 km N of Centro de Investigaciones Jenaro Herrera Requena , 18 November 1988, D. C. Daly, J. Valcarcel, D. Maytehuari, H. Pacaya, O. Mozombite, D. Angulo, R. Canayo 5707 ( NY) ; 21 November 1989, Maytahuari TB P2-2-2 N 184 ( AMAZ) ; Centro de Investigaciones Jenaro Herrera , 4 January 2012, N. Dávila, R. Ortiz, J. Prusky, N. Saavedra, R. García 6318 ( AMAZ) .

Figures

FIGURE 1. Platycarpum loretensis. A. Terminal branch with inflorescence. B. Leaf base with gland at base of petiole. C. Calyx partially dissected showing details of the gynoecium. D. Abaxial face of corolla showing stamens inserted at different heights. E. Fruit. F. Seed. Based on Freitas s/n TB-Cha P 1-II-10. Drawn by Klei Souza.

FIGURE 2. Platycarpum loretensis. Scanning electron micrographs of leaves and pollen. A. Adaxial leaf surface with strigose indument. B. Papillose abaxial leaf surface with tomentose indument. C. Papillose abaxial leaf surface with flaking epicuticular wax. D. Pollen in polar view, showing spherical shape and 4-colp(oroid)ate. E. Reticulated exine (Freitas s.n. P1-II-10).

FIGURE 3. Vegetative details of Platycarpum loretensis. A. terminal shoot showing the discolor leaves. B. stipule. C. internal and external bark (Dávila 6318).

FIGURE 4. Distribution map of Platycarpum loretensis in Peru.