Sticherus holttumii L.V. Lima & Salino, 2018

Lima, Lucas Vieira & Salino, Alexandre, 2018, Sticherus holttumii (Gleicheniaceae, Polypodiopsida), a new species from Brazil, and the first Brazilian record of Sticherus brevitomentosus, Phytotaxa 340 (2), pp. 181-185 : 182

Sticherus holttumii L.V. Lima & Salino , sp. nov. ( Fig. 1 )

Sticherus holttumii is most similar to Sticherus nudus (Moritz in Reichardt 1859: 28) Nakai (1950: 23) and Sticherus pteridellus ( Christ 1906: 284) Copeland (1947: 28) , in having hyaline to stramineous scales on the midribs and secondary veins only. It differs from both mainly by having all axes bearing segments (vs. segments restrict to the ultimate branches), and bud scales lanceolate (vs. bud scales ovate).

Type: — BRAZIL. Pará: Monte Alegre, Trilha para Cachoeira da Prata no Iguarapé do Ambrósio, Mata de Galeria, 1º26’11.5”S, 54º32’40”W, 302 m, 09 December 2015, T. E. Almeida et al. 4174 (holotype BHCB, isotype HSTM).

Plants terrestrial. Stems long-creeping, 2.2–3 mm diam., rugose, sparsely to densely covered with caducous, brown, rigid, linear-lanceolate scales, these 2.8–3.8 mm long, with margins dentate, apices attenuate to filiform, bases truncate or occasionally cordate. Fronds up to 1 m long, occasionally longer, petiole glabrous, 2 mm diam. Laminae up to 3 times forked, often with trifid, small pseudostipules restricted to the first branches. Buds covered with narrowly triangular brown scales, these 1.5–2.5 mm long, with margins dentate, occasionally ciliate, apices filiform, bases truncate. Ultimate branches elliptic, 20–22 × 2.5–4.5 cm, with apices pinnatifid or caudate, bases slightly reduced, with up to 3 reduced segments, rachises abaxially brown, with sparse brown scales, these 0.4–0.7 mm long, margins setose, apices attenuate and occasionally darkened, bases truncate, adaxially glabrous. Segments linear, ascendant, 1.3–2.6 × 0.15–0.24 cm, present on all axes, midribs with linear scales, these with margins setose, secondary veins with arachnoid and stellate scales, these with margins plane to slightly revolute, adaxial surface glabrous. Sori medial. Paraphyses present, hyaline. Spores monolete.

Distribution and habitat: — Sticherus holttumii is known from Pará and Minas Gerais states, in the north and southeast of Brazil respectively, where it grows in gallery forests in Cerrado and Amazonian domains, between 300– 900m. This peculiar distribution pattern is also known from Blechnum heringeri Brade (1966: 87) . The type of this species is from Paracatu, Minas Gerais, as well as one of the paratypes of S. holttumii . Dittrich et al. (2015) mentioned the record of Blechnum heringeri from Pará state, as a disjunct population. It seems that the gallery forests act like a corridor of dispersal for this species. However, more collections are necessary to test this hypothesis.

Etymology: —The epithet is a tribute to Richard Eric Holttum (1895–1990), for his considerable contribution to the knowledge of ferns and lycophytes, especially Gleicheniaceae .

Additional specimens examined (paratypes): — BRAZIL. Minas Gerais: Paracatu, Reserva do Acangaú , 17º08’59”S, 47º04’42.3”W, 665 m, 03 March 2006, A. Salino et al. 10716 ( BHCB) ; Minas Gerais: Grão Mogol, entre a BR 251 e a cidade de Grão Mogol, Cachoeira Véu das Noivas, na Serra de Grão Mogol, Cadeia do Espinhaço , 16º35’43.6”S, 42º57’17.3”W, 875 m, 15 March 2007, A. Salino et al. 11798 ( BHCB) .

Notes: — Sticherus holttumii is morphologically related to Sticherus nudus ( Colombia and Venezuela) and Sticherus pteridellus ( Costa Rica, Guatemala, and Nicaragua) by having hyaline or stramineous scales on segment midribs and secondary veins. Sticherus holttumii differs from both by bearing segments on all axes, while the others usually have segments restricted to the ultimate branches, and by the hyaline paraphyses of the sori. The bud scales of S. holttumii are lanceolate, while in S. nudus and S. pteridellus they are ovate. The margins of the rhizome scales of S. holttumii are dentate, while in S. nudus they are setose and in S. pteridellus entire. Regarding the Brazilian species of the genus, S. holttumii is morphologically similar to Sticherus gracilis ( Martius 1834: 107) Copeland (1947: 27) , with which it shares lanceolate bud scales, caudate apices, and segment sizes. Sticherus holttumii differs from it mainly by the presence of scales on the abaxial surface of segments, while S. gracilis is completely glabrous.

Figures

FIGURE 1. Sticherus holttumii. A. Habit. B. Abaxial surface of rachis. C. Abaxial surface of segment. D. Rachis scale. E-F. Rhizome scale, showing the morphological variation. G. Bud scale.