Epidryos matheusii Sch.Rodr.

Rodrigues, Rodrigo Schütz & Flores, Andréia Silva, 2017, A new species of Epidryos (Rapateaceae) from Guyana, Phytotaxa 297 (2), pp. 197-202 : 200-201

Epidryos matheusii Sch.Rodr. & A.S. Flores, sp. nov. ( Figs. 1–3 )

Epidryos matheusii differs from the other species of Epidryos in having the base of leaf blades gradually passing into a petiole 8–12 cm long, and small inner bracteoles (3–3.5 mm long) and sepals (5–5.2 mm long).

Type: — GUYANA. Potaro-Siparuni: Upper Kuribrong River, 05°20’16” N, 59°33’57” W, 475 m, 18 March 2011, C. E. Zartman, M. M. Pombo, Y. M. Glen & C. Perry 9095 (holotype INPA 241497!, isotype US 3687395).

Epiphyte, caudex 17 × 13 mm. Leaf sheaths 6.7–8.2 × 2–2.3 cm, membranous, many-nerved, conduplicate, auricles absent or poorly developed (up to 2 mm long); base of leaf blades gradually passing into a petiole, 8–12 cm long, 2–3 mm wide; leaf blades 32–41 × 1.4–1.8 cm, linear, acuminate at apex, finely nerved on both sides, the midrib prominent abaxially. Peduncles filiform, 17–20.5 cm long, 0.7–0.8 mm wide, 5–nerved, compressed, except below the inflorescence, where dilated 9–10 mm wide. Inflorescence compressed, 9–12 × 10–14 mm, without involucral bracts. Spikelets 5–7 per inflorescence, 6.3–7 × 2–2.7 mm (including the sepals), fusiform; bracteoles 20–22, obtuse, inconspicuously nerved, chartaceous, brown, darker maculate at apex, gradate, the lower outer ones 0.5–0.7 × 0.7–1 mm, ovate-suborbicular, the upper inner ones 3–3.5 × 1–1.2 mm, ovate-lanceolate. Sepals 3, 5–5.2 × 1.5–1.7 mm, free, lanceolate, acute at apex, subindurate, dark yellow; petals yellow, connate at the base into a tube 1.5–2 mm long, petal blades not seen; stamens 6; filaments 1.5–2 mm long, connate at the base, anthers 2–2.6 × 0.3–0.4 mm, linear-lanceolate, smooth, subsagittate, 2-thecal, 4-loculate, opening by 1 apical pore; ovary 3-carpellate, 1 × 1.5 mm, depressed-globose, style 5 mm long, placentation axial, ovules 5–7 per locule, covered by a mucilaginous, hyaline matrix. Capsule 3.5–3.7 mm long, loculicidal; a single seed seen per locule, seed 1.6–1.8 × 0.9–1 × 0.5 mm, compressed-ellipsoid, testa alveolate, black, partially covered by a white spongy (in a dry state) arillate structure.

Distribution, habitat and phenology: — Epidryos matheusii is known only from Guyana in the riparian zone from upper Kuribrong River at 475m elev. ( Fig. 3 ). Flowers and fruits were collected in March and April. It is the second species of Epidryos recorded for Guyana, with E. guayanensis mentioned for the country by Maguire (1965).

Comments:— Epidryos matheusii is clearly distinct from its congeners, characterized by its long-petioled leaves and small bracteoles and sepals (see key below). It can be separated from E. micrantherus (type: US barcode 00088543!) by its subfiliform peduncles 0.7–0.8 mm wide and anthers 2–2.6 mm long (vs. coarse peduncles 1–1.5 mm wide and anthers 1.8 mm long in E. micrantherus ). Epidryos matheusii differs from the other two species in having spikelets 6.3–7 mm long, whereas E. allenii (type: F barcode V0077973F!) and E. guayanensis (type: NY barcode 00102397!) have spikelets 10–14 mm long.

Epidryos matheusii apparently is restricted to areas in the vicinity of the Kaieteur National Park in Guyana. This region has a high biological relevance, encompassing many different habitats that host several rare species of animals and plants ( Kelloff 2003). According to Kelloff & Funk (2004), 23 species and one genus of angiosperms are endemic to the Kaieteur National Park, including two species of Rapateaceae , Potarophytum riparium Sandwith (1939: 21) and Stegolepis ferruginea Baker (1882: 331) .

Etymology: —It is a pleasure to name this species for our son Matheus, who has been actively helping us in our botanical fieldwork in the Brazilian Amazonia.

Paratypes: — GUYANA. Potaro-Siparuni: Riparian Zone Upper Kuribrong, April 2010, C.E. Zartman, Y.M. Glen & C. Perry 8267 (INPA, UFRR).

Key to Epidryos species (modified from Maguire 1965 and Berry 2004):

1. Base of leaf blades gradually passing into a petiole 8–12 cm long; inner bracteoles 3–3.5 mm long, sepals 5–5.2 mm long............ ............................................................................................................................................................................... Epidryos matheusii

- Leaves lacking petioles; inner bracteoles 6.6–8 mm long, sepals 7–14 mm long..............................................................................2

2. Peduncles subfiliform, 0.5–0.8 mm diam.; inflorescences commonly with 1–3(–6) spikelets..........................................................3

- Peduncles relatively coarse, 1–1.4 mm diam.; inflorescences with (3–)4–7 spikelets.................................... Epidryos micrantherus

3. Bracteoles subindurate, narrowly or not at all scarious; leaf-sheaths ventrally (marginally) ventricose................... Epidryos allenii

- Bracteoles semihyaline, broadly scarious; leaf-sheaths ventrally (marginally) rectilinear .............................. Epidryos guayanensis

Figures

FIGURE 1. Holotype of Epidryos matheusii.

FIGURE 2. Epidryos matheusii. A. Leaf, with its blade gradually passing into a long petiole (arrow). B. Distal part of the peduncle of an inflorescence with six spikelets, one of them in fruit (arrow). C. Detail of a spikelet, with its bracteoles and sepals (arrow). D. Anther. E. Seed partially covered by a white spongy arillate structure (arrow).A–E. C.E. Zartman et al. 8267 (UFRR).

FIGURE 3. Geographic distribution of Epidryos matheusii.