Heteropterys arcuata C. Pessoa & Amorim, 2016

Pessoa, Cleiton & Amorim, André Márcio, 2016, Heteropterys arcuata (Malpighiaceae): a new species from the dry forests of northeastern Brazil, Phytotaxa 260 (1), pp. 83-88 : 85-88

Heteropterys arcuata C. Pessoa & Amorim , sp. nov. ( Figs. 1 , 2 )

Heteropterys arcuata C. Pessoa & Amorim is similar to H. sessilifolia Jussieu (1843: 480) , from which it differs by the petioles 2–4.3 mm long, pedicels 2.5–4.8 mm long, filaments 0.7–1.5 mm long, the samara with an oblique and strongly curved dorsal wing and a nut that is deltoid or rounded, rugose, and without winglets (vs. leaves sessile, pedicels 1.4–3 mm long, filaments 0.4–1 mm long, a samara with an oblique and slightly curved dorsal wing and an ovate nut with lateral winglets in H. sessilifolia ).

Type: — BRAZIL. Bahia: Mun. Palmeiras, road from Palmeiras to Guiné , 12º32’33”S, 41º34’32”W, 718 m, 01 April 2006 (fl., fr.), P. D. Carvalho & A. A. Conceição 302 (holotype HUEFS!; isotype CEPEC!) .

Shrub. Stems cylindrical, 1–3 mm diam., striate, not twisted, glabrous, with minute and sparse lenticels. Leaves opposite; petiole 2–4.3 mm long, eglandular, tomentose to glabrescent with age; stipules ca. 2 mm long, borne on the base of petiole; leaf blade 2.2–5.9 × 1–2.9 cm, membranous, ovate, the base obtuse or rounded, the margins entire or sinuate, slightly revolute in sicco, without ciliae, the apex acute, acuminate or inconspicuously cuspidate, glabrous adaxially, ferruginous tomentose to glabrescent abaxially with T-shaped trichomes, eglandular or occasionally a pair of peltate, ovate glands near base; midvein and secondary veins ferruginous tomentose to glabrescent; secondary veins in 3–4 pairs, arched and grouped near blade margin. Inflorescence erect, paniculate, terminal or axillary, rusty tomentose, 5.5–34 cm long, the flowers borne terminally in congested and dense 4–6-flowered corymbs or umbels, and 3–4 flowers below along the peduncle; inflorescence bracts like leaves, 3.8–9.1 × 2.9–7 mm, ovate, margins entire to sinuate, without cilia, eglandular; peduncle 3–6.5 mm long; bracts 2.1–2.5 × 1–1.5 mm, ovate, eglandular, glabrous adaxially, ferruginous tomentose abaxially; bracteoles similar to bracts but smaller, 1.2–1.7 × 0.8–1 mm, eglandular, inserted just below the apex of the floral peduncle; pedicel 2.5–4.8 mm long, densely tomentose, straight, without broadening towards the apex. Sepals 5, 1.9–2.9 × 1.5–1.9 mm, ovate, distended, connate at base (to each other), the apex rounded, glabrous adaxially, ferruginous tomentose abaxially, the anterior sepal eglandular, the 4 lateral sepals biglandular, the glands 0.6–1 mm long, ovate, glabrous. Petals 5, white to pink, ovate, the margin erose, eglandular, glabrous; posterior petal erect-patent, the claw 1.9–2.7 mm long, the limb 3.9–4.5 × 3.2–4.3 mm, slightly carinate or smooth abaxially; the lateral petals patent to reflexed, the claw 0.9–1.5 mm long, the limb 4–4.7 × 3.3–4.5 mm, abaxially carinate. Stamens 10, glabrous; filaments heteromorphic, 0.7–1.5 × 0.2–0.4 mm, connate to 1/4–1/3; anthers 1–1.8 mm long, unequal, slightly reflexed at anthesis; connectives equally dark (red), eglandular. Ovary 1.5–2 mm long, ovate, sericeous; styles 3, 1.8–2.7 mm long, equaling or exceeding the anthers, glabrous, with lateral stigma, divergent distally between them, the apex rounded to slightly obtuse; the anterior style straight, not arched at the base, slightly shorter than or equal to posterior styles; the posterior styles 2, curvilinear, arched at the base, with the sides of the stigma facing the center of the flower. Samara 18.5–34.2 mm long, red at maturity, sparsely sericeous, with oblique arrangement; dorsal wing 15.5–29.4 × 7.8–10.7 mm, the abaxial edge strongly curved; nut 3–4.8 mm long, deltoid or rounded, rugose, without winglets. Seeds not studied.

Etymology: —The epithet “ arcuata ” (= arched) refers to the strongly curved, inferior dorsal margin of the wings of the samaras.

Notes: — Heteropterys arcuata belongs to H. series Rhodopetalis Niedenzu (1903: 4) . The species of this series are characterized by their short floriferous peduncle, white to pink and carinate petals, generally distended laterally style apices, and the nuts of the samaras generally bearing short lateral crests or winglets ( Niedenzu 1903, 1928, Anderson, 1982). Heteropterys arcuata differs from other species of H. series Rhodopetalis by its 2–4.3 mm long petiole, which is not covered by the base of the leaf, 2.5–4.8 mm long pedicel, 0.7–1.5 mm long filaments, and the samara with an oblique and strongly curved dorsal wing and a nut that is deltoid or rounded, rugose, and without winglets ( Table 1).

Heteropterys arcuata is similar to H. sessilifolia by the habit, leaf pilosity and size, and petal color; however, both can be distinguished (in addition to the characters given in the diagnosis) by the type of leaf indument (tomentose to absent in H. arcuata vs. sericeous to absent abaxially in H. sessilifolia ), the shape and dimensions of the bracteoles (ovate and 1.2–1.7 mm long in H. arcuata vs. ovate-orbicular and 0.8–1.8 mm long in H. sessilifolia ), the posterior petal (with the limb slightly carinate or smooth abaxially in H. arcuata vs. succulent and carinate in H. sessilifolia ) and the nut (without winglets in H. arcuata vs. with winglets in H. sessilifolia ).

Both Heteropterys arcuata and H. perplexa Anderson (1982: 120) have ovate to elliptic leaves, but can be distinguished by the color of the connectives of the stamens that are uniformly dark (red) in H. arcuata vs. uniformly bright (yellow) in H. perplexa . Moreover, H. arcuata is similar to H. caducibracteata Anderson (1982: 118) based on style size and samara color, but these species differ by their bracteoles (1.2–1.7 mm long and ovate in H. arcuata vs. 1.9–2.9 mm long and linear in H. caducibracteata ).

Heteropterys arcuata and H. rubiginosa Jussieu (1840: 278) have rounded to obtuse style apices, but differ by the length of the pedicels (2.5–4.8 mm long in H. arcuata vs. 2.8–7.3 mm long in H. rubiginosa ). Heteropterys rufula Mart. ex Jussieu (1840: 278) is similar because of its peltate glands on the abaxial surface of the leaves and the base and apex of the leaves, but differs by the length of its filaments (0.7–1.5 mm long in H. arcuata vs. 2.2–3.5 mm long in H. rufula ).

Heteropterys arcuata and H. trigoniifolia Jussieu (1833: 83) have similar anther connectives; however, the petals in H. arcuata (posterior petal 3.9–4.5 mm long and lateral petals 4.2–4.7 mm long) are longer than those of H. trigoniifolia (posterior petal 2–2.9 mm long and laterals petal 2.3–3.6 mm long). In addition, Heteropterys pteropetala Jussieu (1833: 31) is similar because of its shrubby habit and some features of its stamens, but can be distinguished by its leaves (usually orbicular and 2–12.7 × 1.1–12 cm in H. pteropetala vs. ovate and 2.2–5.9 × 1–2.9 cm in H. arcuata ).

Distribution, habitat and conservation status: — Heteropterys arcuata is known from the Caatinga (dry forest) biome. This species has been collected twice in the same locality in the state of Bahia and once in the state of Piauí ( Fig. 2 ). According to the IUCN (2012) criteria, H. arcuata should be classified as Critically Endangered (CR [B2 + bi,ii,iii,iv]) due to the following: an area of occupancy less than 10km ²; the areas are in advanced stages of degradation because of agricultural and cattle-raising activities; and the original vegetation is rather impoverished and reduced to small fragments.

Additional specimen examined (paratypes):— BRAZIL. Bahia: Mun. Palmeiras, Palmeiras road to Guiné, 12º36’31”S, 41º34’56”W, 832 m, 24 May 2008 (fr.), P.D. Carvalho & A.A. Conceição 394 (HUEFS!). Piauí: Oeiras, Sossêgo, 7º01’31”S, 42º07’52”W, 10 March 2007 (fl., fr.), F.C.S. Oliveira, L.S. Santana Neto & G. Barros 402 (CEPEC!).

Figures

FIGURE 1. Heteropterys arcuata. A. flowering branch; B. detail of the abaxial surface of the leaf blade; C. bracteole, abaxial surface; D. flower bud, lateral view; E. flower, lateral view; F. posterior petal, lateral view; G. androecium, abaxial view; H. gynoecium, the anterior style in the center; I. detail of apex of the anterior style; J. samara, lateral view; K. detail of the nut, lateral view (all from the holotype; illustration by Lucas Marinho).

FIGURE 2. Distribution map of Heteropterys arcuata (black stars) and H. sessilifolia (black triangles).