Cyathea guentheriana Lehnert, 2009

Lehnert, Marcus, 2009, Three new species of scaly tree ferns (Cyathea-Cyatheaceae) from the northern Andes, Phytotaxa 1, pp. 43-56 : 51-54

Cyathea guentheriana Lehnert , sp. nov. ( Figs. 5 , 6 )

Species affintitate Cyatheae crenatae sed in colore atrociore petiolorum (atropurpureis vs. brunneis) indusiorumque (pallide brunneis vs. albidis), pinnis ascendentibus (vs. pinnis patentibus), absentia squamarum bicolorium indumento laminarum praestans; ab Cyathea squamipede et Cyathea meridensi in pinnis pinnulisque sessilibus (vs. pinnis pinnulisque maximis quidem paulo petiolulatis), marginibus segmentorum valde crenatis vel incisoserratis (vs. marginis crenulatis subintegribusque) differt; dissectione laminarum simile Cyathea xenoxyla sed ab ea soris majoribus (1.0– 1.2 mm vs. 0.8–1.0 mm in Cyathea xenoxyla ), squamis persistentioribus nigribus (vs. squamis brunneis deciduis), petiolis purpureis parce nitentibus (vs. petiolis viridibus vel stramineis usque brunneis opacis), fasciculo petiolorum apice truncorum (vs. fasciculo absente), truncisque crassioribus gemmis adventitiis carentibus (usque 12 cm vs. promedio 5–8 cm diametro, gemmis presentibus) differt.

Type:— ECUADOR. Napo: Quijos Cantón, Reserva Ecológica Antisana, Río Aliso , 8 km SW of Cosanga, 00º35'S, 77º57'W, 2530 m, 12 Nov 1998, Vargas H . et al. 2949 (holotype UC, isotype MO)

Trunks to 6 m tall, to 12 cm diam., without persisting old petiole bases, cortex dark brown to blackish, apices hidden in fascicles of petioles ( Fig. 5 ); without adventitious buds. Fronds to 300 cm long, patent to arching. Petioles 35–100 cm long, proximal parts weakly to strongly spiny, with spines 3–5 mm long, dark brown to atropurpureous, weakly shiny, without adventitious pinnae at the petiole bases, with a discontinuous row of narrowly elliptic pneumathodes to 9 × 1–2 mm, dark orange-brown in dried material; petiole scurf dense, long-lasting, concolorous whitish to tan or pale brown, consisting of small, erect to appressed, ovate to round squamules 0.2–0.5(–1.0) mm long, with strongly crested to fimbriate margins, without dark marginal teeth, only abraded in inermous petiole parts ( Fig. 6A ). Petiole scales lanceolate, 20.0–32.0 × (3.0–) 4.5–5.5 mm, tips straight to falcate, undulate, concordantly bicolorous, bases cordate, pseudopeltately attached ( Fig. 6B ), very shiny, concordantly bicolorous but differentiated margins very narrow and thus at first appearing concolorous, the black (deeply atropurpureous in backlight) centre sharply set against the golden brown margins. Laminae to 200 × 100 cm, bipinnate-pinnatifid, chartaceous, broadest at the middle, dark green adaxially, matte, blackish to plumbeous when dried, dull greyish green abaxially, apices gradually reduced. Rachises dark-purpureous to brown, usually darker adaxially, glabrous or weakly hairy in distal parts; sometimes with remnants of tan to brown scurf, especially in the axils to the costae, consisting of squamules similar to those on the petioles. Pinnae to 55 cm long, 12–15 pairs per frond, inarticulate, ascending, sessile or short-stalked to 0.5 cm, distally not green-alate, the distal segments not decurrently adnate. Costae inermous to muricate, 3–4 mm wide, dark stramineous to purpureous, adaxially often darker, adaxially densely hairy, hairs 0.5–1.0 mm long, tan to brown, antrorsely curved to appressed, abaxially glabrous; junctures of costae and rachises abaxially weakly swollen, each with a planar pneumathode to 4 × 1–2 mm, brown, inconspicious. Largest pinnules 8.0–9.5 × 1.7–2.0 cm, sessile or stalked to 1 mm, alternate, inarticulate, 2.0– 2.2 cm between adjacent stalks, linear-oblong, cuneate to rounded at bases, tapering from beyond the middle to attenuate tips with serrate to crenulate margins ( Fig. 6C ); costules dark stramineous to dark brown, adaxially moderately hairy with appressed tan to brown hairs 0.5–1.0 mm long, abaxially glabrous, rarely with remnants of whitish to tan scurf or with some single erect white hairs to 1 mm long in distal parts; costules basally without pneumathodes; segments to 12.0 × 2.5 mm, linear-oblong, ascending, distally straight to weakly falcate, tips rounded to obtuse, margins deeply crenate to inciso-serrate; basal segments alternate, rarely remote from each other, if so then connected by laminar tissue, sinuses 1–2 mm wide, obtuse; sterile and fertile pinnules not different. Veins glabrous adaxially except for some white to tan, erect pluricellular hairs to 1 mm long on the midveins; abaxially glabrous except for single hairs to 1 mm long sometimes on the midveins; sterile veins forked or simple, fertile veins forked. Sori 1.0– 1.2 mm diam., proximal, indusia subsphaeropteroid to sphaeropteroid, without umbo, tan, translucent, fragmenting to a shallow cup or disc ( Fig. 6D ); receptacles globose, 0.3–0.5 mm diam., paraphyses many, hyaline, tan, shorter than sporangia (0.3–0.4 mm). Spores pale yellow.

Distribution and habitat:— Known only from eastern Ecuador, Prov. Napo, growing at 1920–2530 m in perhumid montane rainforest.

Etymology:—Named after Rebecca Guenther, UC Berkeley, in acknowledgement of her support to tree fern studies.

Additional specimens examined (paratypes):— ECUADOR. Napo: Parque Nacional Sumaco-Galeras, southern slope of Sumaco volcano, 00º35'S, 77°35'W, 1920 m, 06 Apr 2006, Homeier et al. 2243 ( GOET); area of the Yanayacu Biological Station , 5 km SW of Cosanga, 00º36'S, 77º53'W, 2080 m, 21 Oct 2007, Homeier et al. 3093 ( GOET, QCA); Quijos Canton, Reserva Ecologica Antisana, Cordillera de Guacamayos , proposed ARCO oil pipeline route, 00°38'N, 77°51'W, 2000 m, 1 Oct 1997, Neill et al. 10790 ( MO, UC); Tena Cantón, P . N . Llanganates, trail Salcedo-Tena, Km 74, shore of Río Mulatos , 01°01'S, 78°12'W, 2020 m, 10 Sep 1998, Vargas H . et al. 2179 (MO, UC).

With its dark coloration, Cyathea guentheriana resembles other species of Cyathea with sphaeropteroid indusia, like the common C. squamipes Karsten (1869: 184) and C. meridensis Karsten (1861: 199) . These can be easily distinguished by their dark brown to castaneous petiole scurf (in C. guentheriana whitish to pale brown). They further differ from C. guentheriana in the shape of the pinnules and segment margins: In C. squamipes and C. meridensis , the largest pinnules are lanceolate to long-triangular with truncate to weakly cordate bases and the segment margins are crenulate; they are linear-oblong with cuneate to rounded bases and have deeply crenate to incisoserrate margins in C. guentheriana . The pinnae and pinnules of C. guentheriana are usually sessile or very short-stalked; in C. squamipes , the largest pinnules may be stalked to 0.5 cm, in C. meridensis even more than 1 cm. The whole fronds of C. guentheriana seem to be planar and held more or less patent to weakly arching due to the stiff leaf axes, with markedly straight, ascending costae. In C. squamipes and C. meridensis , the fronds are arching to drooping with mostly perpendicular pinnae.

Regarding the fronds, C. guentheriana is best described as C. xenoxyla Lehnert (2003: 175) but with a darker hue. The laminar dissection and the spatial orientation of the pinnae are identical but the petiole scales of C. guentheriana are very shiny, almost concolorous black (vs. weakly shiny dark brown to castaneous with usually paler margins in C. xenoxyla ) and the leaf axes are dark brown to purpureous and weakly shiny (vs. green in fresh material, stramineous to brown in dried material). Cyathea xenoxyla differs significantly from C. guentheriana by having almost no persistent petiole scales (only present in crosiers, rarely on young petioles vs. many persistent scales on the petiole bases in C. guentheriana ), lacking a fascicle of petioles at the trunk apex (vs. fascicle present), having smaller sori (0.8–1.0 mm vs. 1.0– 1.2 mm diameter), and having thinner trunks with adventitious buds (mostly 5–8 cm vs. to 12 cm diam., lacking adventitious buds).

The deeply crenate segment margins, the kind of scurf squamules, the fragile indusia, and the colour and shape of the petiole scales of C. guentheriana agree well with the condition of these characters found in C. crenata ( Sodiro 1883: 18) Christ (1897: 323) (see: Lehnert 2009). The most obvious differences to that species are the darker colour of petioles, rachises, and laminar tissue and the stiffer, notably ascending pinnae. Due to the divergent colour of the petiolar cortex (atropurpureous in C. guentheriana vs. dull brown in C. crenata ), the petiole scurf appears to be lighter coloured in C. guentheriana , but actually has the same colour variation in both species. Furthermore, C. guentheriana has no or only scattered hairs to 1 mm long on the costules abaxially while C. crenata is here often short-pubescent with hairs to 0.6 mm long. The laminar indument of C. crenata includes larger bicolorous flat scales to 5 mm long with dark centres besides smaller, concolorous whitish to pale brown squamules, whereas C. guentheriana lacks bicolorous scales on the laminae. The indusia of both species are very fragile but differ in colour (matte white in C. crenata vs. tan in C. guentheriana ) and consistency (opaque, sometimes developed as mucose film vs. translucent, never a mucose film). Differences in colour and indument are often dependent on growing conditions, especially the exposure to direct sunlight. However, the colour of petioles and leaf axes of C. crenata remains comparatively pale no matter if the species grows in either sun or shade. Cyathea guentheriana has been found only in the shaded understory so far, thus growing under conditions unlikely to add a reddish tone to a relatively pale coloration as it is found in sun-exposed C. crenata .

Despite the apparent mixture of characters typical of several common species in Cyathea guentheriana , there are no indications of a hybrid origin of this species. Sporangia and spores are well formed and of equal size, indicating a regular development involving matching chromosome pairs.

Figures

FIGURE 5. Cyathea guentheriana, trunk apex, Ecuador, Prov. Napo (Photo J. Homeier).

FIGURE 6. Cyathea guentheriana. A. Petiole scurf. B. Petiole scale. C. Pinnule, abaxially. D. Fertile segment, abaxially. All from Vargas H. et al. 2949 (UC).