Dicksonia celebica Lehnert, 2018

Lehnert, M. & Coritico, F. P., 2018, The genus Dicksonia (Dicksoniaceae - Cyatheales) in western Malesia, Blumea 63 (1), pp. 268-278 : 274-275

3. Dicksonia celebica Lehnert , sp. nov. — Fig. 2c , 3b , 4b ; Map 1

This species differs from Dicksonia amorosoana in having a varying amount of thick, dark bristly hairs protruding from the predominantly soft and matted layer of hairs on the petioles. Dicksonia celebica is superficially most similar to D. blumei but has all hairs matted on the rachis (vs mostly spreading in D. blumei ) and has spores with retate perispore (vs smooth). Dicksonia celebica differs from D. mollis in having a relatively voluminous reddish undercoat, and rachises and costae without bristly hairs (vs undercoat thinner, paler on petioles and rachis, and more darker bristly hairs that extend to the distal rachis and often onto the costae in D. mollis ). — Type: F. Brambach 0944 (holo BO; iso BONN, GOET), Indonesia, Sulawesi Tengah, tree-inventory plot ‘Rorekautimbu’, 8.7 km NNE of Sedoa, 800 m N of campsite Puncak Dingin following trail to peak of Rorekautimbu, S01.280° E120.308°, 2420 m, 18–30 July 2011.

Etymology. Refers to the type locality Sulawesi (Latin celebicus = from

Sulawesi).

Tree fern, terrestrial. Trunks to 5.5 m tall, to 17 cm diam, with persistent petiole bases, frond scars not visible; adventitious buds not observed. Fronds to 310 cm long, held erect to ascending in a funnel-shaped crown. Petioles 70–110 cm long (at least 1/3 of frond length), covered throughout with soft, reddish brown to golden, matted hairs, consisting of an outer layer of ciliform hairs to 3.5 cm long with elongate, turgid to collapsed cells and a dense undercoat of paler tortuous, catenate hairs to 5 mm long; largest hairs with indurated bases, most hairs already matted and entangled in live plants, few to copious bristly protruding hairs, leaving a faintly scabrous surface. Laminae to 200 by 130 cm, tripinnate-pinnatifid, base truncate to cuneate, apex gradually reduced, glossy dark green adaxially and light green abaxially, coriaceous, weakly dimorphic with fertile parts more deeply dissected, occurring throughout the lamina. Frond axes (rachises, costae and costules) abaxially covered with similar hairs as on petioles, with pale reddish, matted hairs on rachis, costae and costules, mostly catenate or with catenate bases and dark brown acicular tip, becoming gradually more turgid and spreading towards smaller costules and midveins, adaxially hairs sparser, thin and appressed on rachis and proximal costa parts, becoming shorter and more spreading towards costules, here uniformly whitish, curved, to 1.5 mm long. Pinnae to 65 by 25 cm; fertile pinnae 20–55 by 8–28 cm; subsessile to stalked to 4 cm, lanceolate with truncate bases and attenuate tips, alternate, patent, 8–10 pairs per frond, basal pinnae slightly to notably shorter, at least 1/2 the length of longest pinna. Sterile pinnules to 14.0 by 3.2 cm, lanceolate, subsessile to short-stalked to 1.3 mm, bases truncate to weakly cuneate, apices attenuate; fertile pinnules to 12.0 by 2.5 cm, elongate-lanceolate, subsessile to stalked to 5.0 mm, bases truncate to weakly cuneate, apices attenuate. Sterile segments to 15 by 5 mm, oblong to linear-lanceolate, deeply pinnatifid to pinnatisect, with rounded lobes, the obtuse apices with crenulate margins; fertile segments to 16 by 5 mm, oblong to linear-lanceolate, pinnatisect to basally pinnate, with acute triangular lobes, each bearing one sorus on the acroscopic arm of a branched vein, the sterile apical section rhomboid with serrate margins. Veins of segments adaxially glabrous, abaxially midveins with bicolorous hairs to 2 mm long, with hyaline catenate bases and dark brown acicular terminal cell, lateral veins with few hairs to 1.5 mm long, spreading, hyaline, pale brown to whitish, thin-walled but usually turgid at base. Sori 1.0– 1.6 mm wide, slightly kidney-shaped when closed, circular when open, mostly (c. 75 %) on end of branched vein, the sterile lobe sticking out weakly to strongly below the sorus, if sorus on simple vein (c. 25 %) then on a lobe that is as wide as or wider than the outer indusial valve; indusia bivalved, outer one greenish with a pale brown cartilaginous margin, inner one light brown with entire margins, often shrivelled in dried specimens, both valves may turn darker brown with age or drying but retain a paler margin; paraphyses slightly longer than sporangia, abundant, with pale to red brown clavate tips. Spores tetrahedral-globose, c. 40 µm diam, exospore foveate, perispore papillate-granulate to baculate, presumably deposited in a retate pattern.

Distribution — Indonesia (Sulawesi).

Habitat & Ecology — In upper montane forests, sometimes on exposed sandy ridges, at 1850–2900 m.

Vernacular name — ‘ Sulawesi woolly tree fern’, suggested herewith.

Additional specimens (paratypes). INDONESIA, Sulawesi Tengah, Lore Lindu National Park, Nokilalaki , c. S01°14'12.1" E120°08'32.6", 1850 m, 28 Aug. 2007, Kluge 7542 (UC-1939486); tree-inventory plot ‘ Rorekautimbu’ , 78.7 km NNE of Sedoa , 800 m N of campsite Puncak Dingin following trail to peak of Rorekautimbu, S01.280° E120.308°, 2420 m, 18–30 July 2011, Brambach 0730 ( BO, BONN, GOET); tree-inventory plot ‘ Bulu Torenali’ , 7.7 km NNE of Sedoa, 250 m ESE of campsite Puncak Dingin on mountain crest/ plateau, S01.287° E120.312°, 2350 m, 21–24 Apr. 2012, Brambach 2036 ( BO, BONN, GOET); Enrékang, ridge of Batu Bollong – Madjadja , NNW of Madjadja , 2900 m, 24 June 1937, Eyma 959 ( A,K-000570425,L-959530233, SING n.v.) .

Notes — The spores investigated with SEM ( Fig. 2c ) show hardly any perispore deposit but the collapsed spore walls indicate that the spore was probably young and not fully developed. See further comments under D. amorosoana .

To our knowledge, D. celebica is the only Dicksonia taxon present on Sulawesi. It is known so far only from north-central Sulawesi. Hidayat (2011) surveyed the fern diversity in the south-east of the island and found no Dicksoniaceae . Dicksonia celebica was already recognized as a dubitably distinct taxon by Holttum (1963), who discussed a specimen (Eyma 959) from Sulawesi that “agrees better with D. mollis than with New Guinean species (it is certainly not D. blumei )”. Hovenkamp & De Joncheere (1988) discussed a specimen from the type locality (‘Roroka Timbu’, Hennipman 5262, n.v.) of D. celebica under D. cf. mollis , which differed in having retate spores instead of the verrucose spores that proper D. mollis should have ( Holttum 1962). We have looked at spores from the type of D. mollis and found that under a strong stereomicroscope, the spores may appear verrucose, but the SEM reveals a clear retate layer of perispore ( Fig. 2e ), surrounding clean areoles of the exospore that are usually strongly indented (foveate). We have screened spores of all Malesian species with light microscopes and most also with SEM, and found that species of the Malesian clade (sensu Noben et al. 2017) follow this pattern of spore ornamentation, with some variation in the size of the clean areoles in the retate perispore. The only exception is D. blumei , where the spores appear smooth because the areoles of the exospore are filled up by the copious perispore ( Fig. 2b ).

Superficially, D. celebica could be accommodated as a subspecies under either D. blumei (closer regarding the hairy indument) or D. mollis (matching the spore morphology), but we follow here the molecular evidence that shows D. celebica as the sister taxon to D. amorosoana ( Noben et al. 2017, as ‘ D. cf. blumei ’), separated from the other two species.

Figures

Map 1 Distribution of Dicksonia in western Malesia: D. amorosoana (O), D. blumei (D), D. celebica (Δ), D. ceramica (A), D. mollis () and D. timorensis (z). Map by R. Cámara-Leret.

Fig. 2 Spores of Old World Dicksonia. a. D. amorosoana, distal view, perispore largely lacking, with some mould spore contamination (Philippines, Mindanao); b. D. blumei, distal view, granular persipore filling up retate structure of the exospore (Indonesia, Java); c. D. celebica, proximal view, young spore with perispore only beginning to form near the laesura (Sulawesi, Indonesia); d. D. herberti, distal view (Australia, Queensland); e. D. mollis, distal view (type; Philippines, Mindanao); f. D. sciurus, proximal view (Papua New Guinea) d and f are shown to illustrate the putative fully developed condition of the perispore in a and e, respectively (from: a. Coritico FPC 016, BONN; b. Chen 2040, TAIF; c. Brambach 2036, BONN; d. Kessler 14249, STU; e. Elmer 9874, MICH; f. Lehnert 2886, BONN). — Scale bar: 10 µm.

Fig. 3 Lamina details of Malesian Dicksonia species. a. D. blumei; b. D. celebica; c. D. mollis; a1–c1. sterile pinnules, adaxially (note: a1 from distal part of pinna, b1 and c1 from proximal part of pinna); a2–c2. sterile segments, abaxially; a3–c3. fertile segments, abaxially (from: a. Chen 2040, TAIF; b. Brambach 944, BONN; c. Chen 3837, TAIF).

Fig. 4 Petioles and axes of Malesian Dicksonia. a. D. blumei; b. D. celebica; c. D. mollis; first row (a1–c1) axils between rachis and costa, abaxially; second row (a 2 –c 2) details of petioles, a 2 with hairs partially abraded, exposing the epidermis and the paler softer undercoat, c 2 with most hairs broken off on the right side (from: a. Chen 2040, TAIF; b. Brambach 944, BONN; c. Chen 3837, TAIF).