Cyathea ars Lehnert, 2009

Lehnert, Marcus, 2009, Three new species of scaly tree ferns (Cyathea-Cyatheaceae) from the northern Andes, Phytotaxa 1, pp. 43-56 : 48-50

Cyathea ars Lehnert , sp. nov. ( Fig. 3 )

Species ex grege Cyatheae platylepis , a Cyathea heliophila et Cyathea vilhelmii in squamis petiolorum valde bicoloribus (vs. squamis pallide concoloribus), a Cyathea platylepe paraphysibus longioribus indusiisque minoribus, a Cyathea serpente truncis erectis frondibusque non prostratis (vs. truncis absentibus, frondis supra vegetationem prostratis) differt.

Type:— ECUADOR. Zamora-Chinchipe: Nangaritza, Cordillera de Naguipa, Cerro Colorado , ridge 8 km SSE of Nambija, 20 km ESE of Zamora, 04°07'51"S, 78°46'36"W, 2630 m, 20 Feb 2002, Cole, Delinks & Neill 258 (holotype UC, isotype MO) .

Trunks to 1.5 m tall, otherwise unknown. Fronds to ca. 1 m long. Petioles to 20 cm long, probably more, dull brown to orange-brown, inermous, scurf persistent, white to tan, consisting of many tortuous white hairs to 2 mm long, grading into brown, subbullate squamules with few white, long, apical cilia, persistently densely scaly throughout; pneumathodes absent or not evident. Petiole scales to 16 × 5 mm, lanceolate-ovate, shiny, strongly bicolorous, discordantly so in lower parts, concordantly in upper parts of the petiole ( Fig. 3A ), dark castaneous with yellowish to cream-white margins; differentiated margins to 1 mm wide, fragile, lacerate to erose, with cells strongly exerted, without setae or cilia. Laminae to ca. 80 × 100 cm, bipinnate-pinnatifid to tripinnate, chartaceous, matte, dark green adaxially, blackish when dried, pale grey-green abaxially, apices gradually reduced. Rachises inermous, with many spreading ovate scales similar to petiole scales but with narrower margins; adaxially with many appressed, brown, pluricellular, uniseriate hairs 1.0(–1.5) mm long, abaxially glabrescent with white scurf like on the petioles, but whitish to brown squamules more numerous and with more white marginal cilia than those on the petioles; junctures of rachises and costae not swollen, abaxially each with one planar, brown, elliptic pneumathode to 2 × 1 mm. Pinnae to 50 cm long, stalked to 2.5 cm, inarticulate, patent to ascending ( Fig. 3B ), basal pinnae only half the size of medial pinnae, weakly to strongly reflexed. Costae inermous, 1.5–2.0 mm wide, dull dark brown to carnose, short-hairy adaxially, hairs to 1 mm long, pluricellular, tan to brown, antrorsely curved, abaxially glabrescent with scurf and few darkbrown, flattish scales with undulate margins. Largest pinnules 5.0–6.5 × 1.1–1.7 cm, lanceolate to longtriangular, pinnatifid to pinnate, subsessile to stalked ( Fig. 3C ), stalks to 5 mm, decurrently green-alate, 1.0– 1.5 cm between adjacent stalks; pinnule bases truncate to weakly cordate, tips long-acute to attenuate, basal segments sometimes remote and rarely free; costules dark brown to dark carnose, strongly prominent and ridged adaxially, with tan to brown, antrorsely curved hairs to 1 mm long, abaxially weakly prominent, with tortuous hairs to 2 mm long, tan to dark brown squamules attenuate to caudate tips and with white marginal cilia, and some ovate to almost round, pseudopeltately attached, shiny brown scales to 4 × 3 mm; costules basally without pneumathodes; segments to 9 × 3 mm, oblong, basal ones sometimes free and remote, patent to weakly ascending, straight or distally falcate, the tips obtuse to rounded, segment margins crenulate to incisocrenate ( Fig. 3C ), in proximal segments usually basiscopically more strongly dissected, sinuses acute to obtuse, to 1(–1.5) mm wide, margins often still planar when dried; midveins adaxially ridged, lateral veins planar, veins adaxially glabrous or with few erect, pluricellular, uniseriate hairs and ephemeral tortuous hairs, none between the veins, abaxially with tortuous white hairs, midveins also with few brown bullate squamules to 3 mm long with white apical cilia ( Fig. 3D ); sterile veins forked or simple, fertile veins forked. Sori to 1.0 mm diam., subproximal, at vein forks; indusia hemitelioid ( Fig. 3D ), dark brown, shiny, firm, ascending, with emarginate margins, sometimes weakly bicuspidate, reaching 1/3 to 1/2 around the receptacles, covered entirely by intact sori; receptacles globose, 0.3–0.4 mm diam. ( Fig. 3D ), paraphyses thin, hyaline, tan, shorter than sporangia (0.2–0.3 mm). Spores not examined.

Distribution and habitat:— Known only from the type locality in Ecuador, Prov. Zamora-Chinchipe, where it grew open heath forest on sandstone derived soils.

Etymology:—The name refers to the artful pattern the scales create on trunks and petioles. The name is a noun in apposition.

Cyathea ars is superficially similar to C. heliophila Tryon (1986: 43) , from which it differs in distinctly bicolorous petiole scales (vs. mainly concolorous white or with small brown basal spot in C. heliophila ) and many concolorous brown, ovate to round scales on the leaf axes (vs. white to bicolorous, ovate-lanceolate scales).

Cyathea serpens ( Tryon 1989: 126) Lehnert , comb. nov. (basionym: Trichipteris serpens Tryon ), from central and southern Peru differs from C. ars by lacking trunks and having much longer fronds (to 7 m vs. ca. 1 m long) that scramble over adjoining vegetation or hang freely from cliffs.

Cyathea platylepis can be distinguished form C. ars by its concolorous brown petiole scales (margins only slightly paler than centres vs. margins white in C. ars ) and the large indusia that arch over the sori (vs. indusia small and hidden by intact sori).

Cyathea ars is characterized by tortuous white hairs and brown scales on the leaf axes, which are also found in C. frigida ( Karsten 1859: 61) Domin (1929: 262) ; that species is exindusiate and has dark brown, only weakly bicolorous petiole scales with brown margins (vs. hemitelioid indusiate and strongly bicolorous petiole scales with white margins in C. ars ).

Cyathea ars occurs sympatrically with C. heliophila and C. frigida . There are several fertile specimens of putative hybrids between C. heliophila and C. frigida , coincidentally all of them from trunkless plants. Fertility in trunkless plants is known from C. frigida but not from C. heliophila . The plants in question have the appearance of a small C. heliophila with strongly bicolorous petiole scales that appear intermediate between the two putative parents (with the white margins inherited from one parent and the dark brown centre of the other. The main indicator for hybrid origin is, apart from intermediate morphology, the irregularly developed sporangia and the malformed spores. The single collection of C. ars has immature sporangia, so an investigation of aborted or malformed spores as indicator of hybrid origin is not possible. However, the abundant laminar squamules of C. ars with their attenuate to caudate tips and white marginal cilia are quite unique in the genus and not interpretable as an intermediate or inherited character from either putative parent. Cyathea ars belongs to the neotropical species referred to as the C. multiflora Smith (1793: 416) group ( Tryon 1976). The group is held together only by the presence of hemitelioid indusia. Like all indusial characters, it is a homoplastic character that does not necessarily include all descendents of one common ancestor. A gross distinction among the species of the C. multiflora group can be made between those species with ± medial to inframarginal sori and those with proximal sori. Cyathea ars belongs to the latter group, together with C. platylepis ( Hooker 1861: 100) Domin (1929: 264) , C. arnecornelii Lehnert (2003: 178) , C. heliophila , C. holdridgeana Nisman & L.D.Gómez ( Gómez 1971: 168) , C. praeceps Smith (1990: 253) and C. vilhelmii Domin (1929: 263) . These species further agree in having inermous petioles, the clean shedding of the old petioles, lacking fascicles of petioles around the trunk apex, and having relatively broad, ovate lanceolate scales with short-acute apices on the trunk and petioles. The collectors did not describe the habit of Cyathea ars (a picture of the plant was taken but was not available for this study) but it is presumably concordant with its supposed closest relatives. The group with medial to inframarginal sori, to which C. multiflora and C. andina ( Karsten 1856: 452) Domin (1929: 263) belong, has muricate to aculeate petioles, do not shed the old petioles cleanly (bases persist), trunk apices hidden in a fascicle of petioles, and petiole scales with long acuminate to attenuate apices (breadth of scale body varies from narrowly to broadly lanceolate).

Figures

FIGURE 3. Cyathea ars. A. Petiole scale from petiole base. B. Medial pinna. C. Fertile pinnule. D. Fertile segment abaxially. All from Cole et al. 258 (A, C-D: UC; B: MO).