Meniscium divergens R.S.Fernandes & Salino, 2014

Fernandes, Rozijane Santos, Yesilyurt, Jovita Cislinski & Salino, Alexandre, 2014, New species and combinations in Meniscium (Thelypteridaceae), Phytotaxa 184 (1), pp. 1-11 : 2-4

Meniscium divergens R.S.Fernandes & Salino , sp. nov. (Figs. 1A–D; 3A; 4C–D)

Meniscium divergens is most similar to M. nesioticum ( Maxon & Morton 1938: 362) Jermy & Walker (1985: 276) , with which it shares dimorphic fronds, and M. cocleanum ( Smith & Lellinger 1985: 918) R.S.Fernandes & Salino , with which it shares pinnae that are glabrous abaxially. It differs from these species mainly by the presence of 5–6 pinnae pairs, 5–6 rows of areoles between the costa and pinna margin in sterile pinnae and 3–4 areole rows in fertile pinnae, sori on the cross-veins, sori not confluent at maturity, and sporangial stalks with trichomes.

Type:— GUYANA. Potaro-Siparuni Region: Pakaraima Mts, Mt. Wokomung top slope 0.5–2 km NW from northern escarpment, 05°04’N, 59°53’W, 1300–1400 m, 13 November 1993, T. W . Henkel et al. 4368 (holotype NY, isotypes NY, US).

Plants rupicolous or terrestrial. Rhizomes short-creeping. Fronds dimorphic, the fertile with longer petioles and pinnae smaller and narrower than sterile ones; sterile fronds 45–97 cm long, petiole 21–42 cm long and 2.5–3.8 mm in diameter at base, laminae 24–53 cm long, pinnae 15.0–21.5 × 2.4–3.6 cm, oblong-lanceolate; fertile fronds 73–105 cm long, petioles 53–61 cm long and 2.3–3.6 mm in diameter, at base laminae 20–44 cm long, pinnae 10.5–17 × 1.0– 1.8 cm, linear lanceolate. Petiole brown at base, stramineous to greenish further up, glabrous. Laminae 1-pinnate, membranaceous. Rachis glabrous. Buds absent. Aerophores absent. Pinnae 5–6 pairs, short–petiolulate (1.6–3.1 mm long) to sessile in the distal pinnae, base rounded to cuneate in the basal pinnae, and asymmetric (basiscopic side rounded and acroscopic side excavate and parallel to the rachis) in the distal pinnae, margin entire or undulate, apex acuminate to caudate; adaxial surface of costae glabrous or sparsely pubescent, with acicular to ciliform trichomes mostly 0.2–0.3 mm long, veins and laminar surface between the veins glabrous, abaxial surface of costae, veins and laminar surface between the veins glabrous; venation regularly anastomosing, forming 5–6 areole rows in sterile pinnae and 3–4 areole rows in fertile pinnae between costae and pinnae margin, veins arising from costae of fertile pinnae ca. 10–12 and sterile 8–9 per 3 cm; cross-veins arcuate (fertile) or subsinuate (sterile), uniting at an obtuse (fertile) or acute (sterile) angle, giving rise to a free excurrent veinlet. Sori oblong, on the cross-veins, not confluent at maturity, receptacle setose with acicular trichomes; sporangial stalks glabrous or with acicular trichomes to 0.3 mm long. Spores monolete, ellipsoidal, with echinulate surface with low, dense echinulae.

Distribution and Habitat:— Meniscium divergens is endemic to the Guayana Shield, with collections only from the Potaro-Siparuni Region ( Guyana) where it apparently grows inside or along the edges of cloud forests in soils with thick layers of organic matter on brown sand and with occasional sandstone outcrops at 700–1400 m.

Etymology:— Epithet refers to the dimorphism of the fronds.

Additional specimens examined (paratypes):— GUYANA. Potaro-Siparuni Region : Mt. Ayanganna , east face, base of first of three escarpments. 05°20’04’’N, 59°55’30’’W, 712 m, 4 June 2001, H.D. Clarke et al. 8961 ( NY, US); same locality, 30 June 2001, H.D. Clarke et al. 9677 ( NY, US) .

Notes:— In the genus Meniscium , only three species have dimorphic fronds— Meniscium macrophyllum Kunze (1839: 44) , M. nesioticum , and M. divergens —and they all occur in Guyana. Meniscium macrophyllum and M. nesioticum are distinct from the new species in having acrostichoid sori and pilose abaxial surfaces of costae and veins. In addition, M. macrophyllum has sterile pinnae 5.7–7.8 cm wide, fertile pinnae 2.7–3.2 cm wide, and oblong to elliptic pinnae. M. nesioticum has 7–11 pinnae pairs, fertile pinnae with 6–13 areole rows between costae and margin, fertile lamina with curved trichomes on abaxial side of costae, sori usually appearing to cover the lamina (acrostichoid) and sporangia glabrous. In comparison, M. divergens has sterile pinnae 2.4–3.6 cm wide, fertile pinnae 1.0– 1.8 cm wide, and linear–lanceolate to oblong pinnae, as well as 5–6 pinnae pairs, fertile pinnae with 3–4 areole rows between costa and margin, fertile laminae glabrous abaxially, sori oblong, on the cross–veins, not confluent at maturity (Fig. 1A–D), and sporangia stalks with acicular trichomes (Fig. 3A).

Although with a distinct geographical distribution ( Panama, Costa Rica and Nicaragua), Meniscium cocleanum is most similar to M. divergens in having both sides of laminar surface between the veins glabrous but differs by the presence of buds on the axils of the distal pinnae, 7–10 areole rows between costa and margin in fertile pinnae, and glabrous sporangia.

The spores have not been used to distinguish species within Meniscium in the past. However, they provide good characters, not only at the generic level ( Tryon & Tryon 1982) but also for separating closely related species. Spores of M. divergens are echinulate (Fig. 4C–D), cristate-reticulate in M. nesioticum (Fig. 4E–F) and winged in M. cocleanum (Fig. 4A–B).

FIGURE. Meniscium divergens . A. Habit. B. Detail of the abaxial surface of fertile pinnae showing sori oblong on the cross-veins. C. Detail of the abaxial surface of sterile pinnae showing venation. D. Detail of a sorus showing acicular trichomes. (A from H.D. Clarke et al. 9677 NY; B–D from T.W. Henkel et al. 4368, NY)

FIGURE. Meniscium triangularis . A. Habit. B. Detail of the abaxial surface of fertile pinnae showing sori round on the cross-veins. C. Detail of the abaxial surface of costae showing trichomes and scales. D. Scales of the abaxial surface of costae and veins. (All from W. D. Rodríguez et al. 4115, NY)