Sticherus fuscus J. Gonzales 2011, sp. nov.

Sticherus fuscus J.Gonzales, sp. nov. (Fig. 10)

Sticherus species statura pro genere media, pinnae 15–30 cm longae, aphlebiae breves, simplices. Rhachides squamulis fuscis persistentibus provisae, rhachides distales breves, blade anceolata, segmentis planis indumento (in pagina abaxiali) dense arachnoideo rufo-brunneo, rhachides abaxiales squamis lateralibus fuscis instructae.

Type: — COSTA RICA. Limón: Cordillera de Talamanca, Atlantic slope, Cerro Tararia, 2400–2600 m, 10 September 1984, Davidse 28845 (holotype MO!, isotype CR!).

Rhizomes unknown. Petioles 2–3 mm thick, reddish brown, brittle. Rachises ca. 14 cm long between pinnae, weakly scaly, the scales erect, dark brown, aphlebiae short, simple. Fiddleheads ca. 3 mm in diameter, matted, the scales dense, spreading, orange to dark reddish brown. Buds ascending and opening rapidly, the scales lanceolate, 1.6–2.6 × 0.4–0.6 mm, brilliant orange to reddish brown, the margins with short setulae or with cilia 1/10 times the scale length, rigid, translucent to matte, with clear and hexagonal or ill-defined and dark cells. Pinnae 15–30 cm long, 2–3-forked, 1 st branch 3.5–5.0 cm long and ca. 2 mm thick, not pectinate, 2 nd branch 1.5–3.0 cm long and ca. 1.5 mm thick, with gradually reduced, usually overlapping internal segments, 3 rd branches 12–20 cm long and ca. 1.5 mm thick, fully pectinate–pinnatisect, narrowly lanceolate, 2.0– 3.5 cm wide with segments, with 2–3 segments per cm; adaxial scales deciduous, mixed, one type rectangular, ca. 0.20 × 0.05 mm, the second type arachnoid, 0.05 mm in diameter, both scale types orange to whitish, translucent; abaxial scales lateral, narrowly lanceolate, apically fringed, 1–2 × 0.3–0.4 mm, brilliant orange to reddish brown, the margins with cilia 1/5 times the scale length or with short setulae, basally translucent and usually with rigid apices. Segments oblong, chartaceous, 1.0– 3.2 cm × 1.0– 1.5 mm, flat; adaxially glabrous; abaxially densely scaly on midveins and veinlets; midvein scales mixed, one type linear, 1–2 × 0.01– 0.05(–0.10) mm, orange, translucent, the margins with few cilia, the second type triangular to square, 0.3–0.6 × 0.3–0.4 mm, orange to dull brown, the margins with cilia 1/2 times the scale length, translucent with rigid apices, the cells square to irregular; veinlets raised, covered with scales, the scales arachnoid, matted, brilliant orange to reddish. Sori inframedial, nested within arachnoid scales, 6–15(–27) pairs per segment, 3–5 sporangia per sorus.

Distribution and ecology: —Endemic to the Cordillera de Talamanca in Costa Rica; to be looked for in adjacent Panama. Known from only two collections in disturbed humid montane forests (with Quercus spp.) at 2400–2500 m.

Specimen examined (paratype): — COSTA RICA. Cartago: SE of Empalme, 9°42’N 83°53’W, 2500 m, 17 March 1973, Stolze 1380 (US).

Notes: — Sticherus fuscus is a medium-sized species with pinnae 15–30 cm long, short, simple aphlebiae, persistent dark scales on the rachises, rather short, lanceolate distal branches with flat segments, and abundant, dark lateral scales on the abaxial branches. These dark axial scales contrast with the dull brown arachnoid scales of the segment surfaces. The bud scales are narrowly lanceolate and mostly rigid with translucent bases, whereas the midvein scales are rectangular and only apically rigid (especially the proximal ones).

Sticherus fuscus may be confused with S. brevipubis, S. tepuiensis, S. aurantiacus, and S. fulvus. Sticherus brevipubis differs from S. fuscus in being generally larger, having much more reduced aphlebiae (or even lacking aphlebiae), reduced internal proximal segments on all branches (i.e., the segments do not overlap as in S. fuscus), more revolute segment margins, and paler segment scales. Sticherus tepuiensis lacks aphlebiae, has narrower and longer branches, glabrous rachises, and has shorter and scattered lateral scales abaxially on the branches. Sticherus aurantiacus differs in having longer, more linear distal branches, reduced proximal internal segments, and has scales of generally paler, duller colors and thinner texture. The pattern of scale darkening of S. fuscus resembles that of S. fulvus, and specimens with strongly rigid scales of the latter species may be confused with S. fuscus. However, S. fulvus is generally larger, has shorter and more ovate scales, more strongly reduced, auricle-like, non-overlapping proximal internal segments, and usually lacks aphlebiae.

Sticherus fuscus is known only from two collections from Costa Rica. It is very unlikely that the type specimen represents a hybrid, because the only potential parental taxa in Costa Rica would be S. brevipubis and S. ferrugineus and the known hybrids between these two species are much larger than S. fuscus and have larger aphlebiae. The confusion surrounding this species complex (see also Stolze 1981) can be resolved only through a detailed biosystematic study involving cytotaxonomic and molecular data.