Parablechnum prostratum J. Murillo & L.A. Triana, 2023

Murillo-A, José & Triana-Moreno, Luz A., 2023, A new species of Parablechnum (Blechnaceae) with prostrate leaves, Phytotaxa 603 (2), pp. 184-190 : 184-188

Parablechnum prostratum J. Murillo & L.A. Triana , sp. nov.

(Fig. 1,2).

Type: COLOMBIA. Putumayo, San Francisco, carretera de Pasto a Mocoa , Vereda Los Monos , km 93–94, cerca al restaurante El Refugio, 1°5’6.7”N, 76°49’58.4”W, 2218 m, 22 feb 2023, J. Murillo et al. 4901 (holotype COL!, Isotypes FAUC!, PSO!) .

Diagnosis:— Parablechnum prostratum is recognized by having prostrate, rosulate sterile leaves, appressed to the substrate, petioles and rachises densely covered with scales of variable size and shape and entire to dentate margin; generally cylindrical aerophores (1–) 2–3 mm long; pinnae revolute, close to each other, touching on their margins, and abaxially covered with abundant scales on the middle vein. The fertile leaf is erect, the pinnae linear with cordate, bulliform bases, wider than the rest of the pinna.

Terrestrial or rupicolous, rhizome erect, ca. 5 cm long; densely covered with ovate 6–11 (–25) × 2–4 (–5) mm, brown, with long-acuminate apex, basifixed, entire, opaque scales. Dimorphic leaves, the sterile ones prostrate, rosulate; petioles 3–11 (–27) cm in length, 1.5–2 (–10) mm in diameter, adaxially grooved, light brown to dark brown, transversely papillose, sometimes smooth; densely covered with ovate to ovate-lanceolate scales of two sizes, some (6–) 9–10 (–25) × (1.5) 2–2.5 (–5) mm, others 1–2 × 0.2–0.6 (–1) mm, brown, with acuminate to long-acuminate apex, margins entire to denticulate, with sparse teeth ca. 0.2 mm long; laminae 23– 32 (–40) × 6.5–10.5 (–13.5) cm, pinnate, elliptical; rachis stramineous, sometimes atropurpureous, transversely papillose; densely covered with brown, ovate scales of three types: (i) linear-ovate, 7–9 × 1.5–2 mm, with filiform apex, margin entire or with sparse teeth, (ii) ovate, 3–3.5 × 1.2–1.5 mm, with dentate margin; (iii) linear, 1–1.5 × 0.1–0.2 mm, with sparse, long teeth 0.3–0.5 mm long; buds absent, aerophores present, cylindrical or sometimes bacillate or reniform, ca. (1–) 2–3 mm long, shorter distally; pinnae (11–) 23–32 (–41) pairs, close to each other, usually touching each other, perpendicular to the rachis, sometimes the basal pair slightly deflected; oblong, falcate, 3–5 × 0.8–1.2 cm, chartaceous, with rounded apex, cordate base, equilateral, margin entire, sometimes serrated, revolute, sometimes strongly revolute when dry; adaxially covered with abundant to sparse, linear to rounded scales 0.5–0.8 mm, with long marginal teeth 0.2–0.5 mm long; middle vein abaxially densely covered with ovate scales, 2–3 × (0.5–) 1–1.2 mm, apex acuminate to long-acuminate, with sparse teeth, distally covered with abundant scales similar to those adaxially present; petiolules stramineous, sometimes adaxially atropurpureous in basal pinnae, 1–2 mm long; veins free, simple, sometimes furcate at their bases, sometimes adaxially elevated when dry, flat to immersed abaxially, ending in conspicuous hydathodes. Fertile leaves erect, with petioles proximally dark brown, yellowish with dark brown blotches in the middle portions, and stramineous distally, sometimes dark brown through their entire length, 7–10 (–26) cm long, 3–4.5 (–12) mm diam., adaxially grooved, densely covered with scales similar to those on the petioles of sterile leaves; laminae 17–23 (–41) × 4–5.5 (–9) cm, pinnate, elliptical, with truncate base, covered with abundant scales similar to those of sterile laminae; rachis stramineous, adaxially grooved, with cylindrical aerophores 2.2 mm long, distal ones 1.2 mm long; pinnae (16–) 19–29 (–35) pairs; linear, 2–3 × 0.3–0.4 cm, chartaceous, with obtuse to rounded apex, base cordate, wider than the rest of the pinna, bulliform, 5–7 mm wide, equilateral; margin entire, densely covered with scales similar to those of the sterile pinnae; petiolules dark brown 1–2 mm long; veins free, inconspicuous, ending in inconspicuous hydathodes. Indusium elongated, brown, erose, glabrous to abundantly covered with linear scales 0.7–0.8 mm long, with few medial and basal prolongations ca. 0.5 mm long. Spores light brown, perine reticulated, with large areoles.

Habitat and distribution: — This species has been recorded in the Cauca, Nariño, and Putumayo departments of Southern Colombia ( Fig. 3 ), between the Andean forest and paramo, at elevations from 1,500 to 3,400 m. It grows on cliffs in zones with high humidity and associated with a dense cover of bryophytes. The rhizome is erect, ca. 5 cm long, making its way between associated bryophytes, so that leaves grow prostrate on the bryophyte layer. It is possible that leaves look pendulous, but this is due to the strong slope of the places where it grows.

Etymology: —The species epithet refers to the prostrate growth of sterile leaves, a unique character within the genus.

Examined specimens: — COLOMBIA. Cauca: Páramo de Puracé, 3400 m, 22 Sep 1967, W. Hagemann 561 ( COL); 10 km east of Puracé (27 km east of Popayán ), 3200 m, 4 Oct 1961, R. Tryon 5961 ( COL). Nariño: NE ridge of Cerro Gualcalá, 18 km N of E of Piedrancha, 1º 7–11’N–77º 43–45’W, 3200 m, 4–6 Oct 1943, F. Fosberg 21163 ( COL). Putumayo: 50 km west of El Pepino, 2050 m, 20 Nov 1972, W. Hagemann 1548 ( COL, PSO); Pasto-Mocoa road, between El Mirador and San Francisco, 1500–2200 m, 27 Nov 1967, L. E. Mora 4455, 4467 ( COL); Mirador, ca. 2000 m, 26 Nov 1969, W. Schwabe C1 69/077 ( COL); San Francisco, carretera de Pasto a Mocoa, Vereda Los Monos, km 93–94, cerca al restaurante El Refugio, 1°5’4”N, 76°49’51”W, 2196 m, J. Murillo et al. 4900 ( COL, FAUC, PSO).

Notes:—The new species described herein undoubtedly belongs to Parablechnum . It features defining characters for the genus: it has pinnate laminae, with petiolulate pinnae and conform apical pinnae, and lacks reduced pinnae at the base ( Figs. 2 A-D) ( Gasper et al. 2016, Molino 2022). Another character that has also been found in some species of Parablechnum , and that is also in the new species proposed here, is the presence of six meristeles at the base of the petiole, two enlarged on the adaxial side and the remaining on the abaxial side smaller and arranged in an arc ( Fig. 2 F ) ( Rolleri et al. 2012). Parablechnum prostratum is unique within the genus because of the prostrate and rosulate growth of its sterile leaves, which are appressed to the substrate. The other species in Parablechnum with prostrate leaves is P. procerum (G.Forst.) C.Presl from Oceania, with leaves with 1 to 12 pairs of pinnae ( Brownsey & Perrie 2021). This species could sometimes be prostrate, but in general it has suberect and arching leaves, even on the same plant both prostrate and suberect leaves can occur ( Brownsey & Perrie 2021). All other species of Parablechnum feature erect to arched leaves ( Molino 2022). Within Blechnaceae , the prostrate distribution of the leaves has also been described in Struthiopteris spicant (L.) Weiss ( Rolleri & Prada 2006), apparently a character that is not constant, because Molino et al. (2019) do not mention it for this species, but they do for Spicantopsis . Additionally, several species from New Zealand have been described by Brownsey & Perrie (2021) with sterile leaves in a prostrate to suberect rosette, including Austroblechnum banksii (Hook.f.) Gasper & V.A.O.Dittrich , Austroblechnum lanceolatum (R.Br.) Gasper & V.A.O.Dittrich , Austroblechnum membranaceum (Colenso ex Hook.) Gasper & V.A.O.Dittrich , Cranfillia fluviatilis (R.Br.) Gasper & V.A.O.Dittrich , Cranfillia nigra (Colenso) Gasper & V.A.O.Dittrich , Doodia mollis Parris , Doodia squarrosa Colenso , Lomaria discolor (G.Forst.) Willd. However , in the analysis of the images of live plants shown by Brownsey & Perrie (2021) only the prostrate growth and in contact with the substrate is observed in A. banksii , A. membranaceum and C. nigra . Undoubtedly, P. prostraum does not belong to any of these genera.

Other character present in P. prostratum is that the bases of fertile pinnae are bulliform, making them wider than the rest of the pinna. Several species from Oceania, such as Parablechnum camfieldii (Tindale) Gasper & Salino , P. confusum (E.Fourn.) Gasper & Salino , P. dilatatum (Brause) Gasper & Salino , P. novae-zelandiae (T.C.Chambers & P.A.Farrant) Gasper & Salino , and P. subcordatum (E.Fourn.) Gasper & Salino , as well as P. pacificum (Lorence & A.R.Sm.) Gasper & Salino , from the Southern Pacific, and sometimes P. wohlgemuthii K. Kessler & A.R. Sm. , from Bolivia, also have fertile pinnae with broadened bases ( Molino, 2022). However, in these species the bases of pinnae are flattened (vs. bulliform) and leaves are erect to arched (vs. prostrate). The new species is very similar to P. moranianum (A. Rojas) Gasper & Salino from Costa Rica ( Rojas 2006) in leaf size and shape, as well as the scale shape and distribution on the lamina. However, the latter species has erect and arched sterile leaves (vs. prostrate) and sterile pinnae are separated (vs. touching by their margins). Cylindrical aerophores in the new species resemble those of Parablechnum chiriquanum (Broadh.) Gasper & Salino , but in this species sterile leaves are erect (vs. prostrate), pinnae are flattened (vs. revolute) and leaves are generally larger (> 70 cm vs. <67 cm). Laminae are similar to those of Parablechnum lima (Rosenst.) Gasper & Salino , but the latter has tuberculiform aerophores and erect leaves. The leaves also resemble those of P. stuebelii , but this species has largely reptant rhizomes, with erect leaves distributed along the rhizome.

Figures

FIGURE 2. Parablechnum prostratum. A. Habit, B. Juvenile sterile leaf, C. Fertile leaf, D. Petiole and lamina scales, E. Detail of the rachis showing the aerophores (white circles), F. Cross section of petiole, showing six meristeles (white arrows), G. Detail of the abaxial surface of fertile pinnae, H. Rhizome scale, I. Petiole scale, J-K. Pinna scales. Photos by J. Murillo and L.A. Triana.

FIGURE 3. Distribution map of Parablechnum prostratum. Modified from QGIS v 3.18.3-Zürich (http://qgis.org).