Alsophila weidenbrueckii Lehnert, 2016

Lehnert, M., 2016, Alsophila weidenbrueckii (Cyatheaceae), a new scaly tree fern from Papua New Guinea, Blumea 61 (1), pp. 20-23 : 21

Alsophila weidenbrueckii Lehnert , sp. nov. — Fig. 1

A newly recognized species of Alsophila with sphaeropteroid indusia, bipinnate-pinnatifid to tripinnate laminae and fine scurf of setate squamules which stands out among its most similar congeners A. archboldii (C.Chr.) R.M.Tryon and A. foersteri (Rosenst.) R.M.Tryon by having dark brown petioles and frond axes (vs stramineous to pale brown), smaller petiole scales (c. 11 by 2 mm vs to 20 by 3 mm) and a sparser indument of smaller setate squamules on midveins and veins abaxially (to 0.2 mm long vs mostly 0.5–1 mm long, characteristically dense in A. archboldii , variable in A. foersteri ). Alsophila weidenbrueckii further has long petioles that shed cleanly from the trunk (just as in A. archboldii vs petiole bases persisting in A. foersteri ) and basal pinnae that are not greatly reduced in size (usually more than half the length of longest pinna, just as in A. archboldii vs pinnae basally tapering in A. foersteri ). — Type: M. Lehnert 2900 (holotype BONN (3 sheets); isotypes LAE,Z), Papua New Guinea, Madang, Madang District,plot sites of Binatang Research Center above Bundi, S05°45.337' E145°11.170', 1700 m, 8 Aug. 2014. Sterile plant with trunk 0.6 m tall; fertile parts distributed under this number come from a fragmentary collection of an adjacent plant 4 m tall and are to be treated as M. Lehnert 2900 bis.

Epitype. M. Lehnert 2900 bis (holoepitype BONN; isoepitypes LAE, Z) , Papua New Guinea, Madang, Madang District, plot sites of Binatang Research Center above Bundi , S05°45.337' E145°11.170', 1700 m, 8 Aug.2014 .

Paratype. Papua New Guinea, Madang Province, Madang District, between Plot 3T-P26 and P 29 , S05°45.625' E145°11.184', 2065 m, 4Aug.2014, M . Lehnert 2889 ( BONN, LAE, Z) .

Etymology. The species is dedicated to Barbara Weidenbrück of Bonn,

Germany, in recognition of her friendship and support of botanical studies.

Tree fern. Trunk to at least 6 m tall, erect, without old petiole bases, to 7 cm diam; pale reddish brown to stramineous scales dense on the exposed apex between the petioles and on the croziers, sparser in lower parts, long persisting as a fine cover of easily abraded pale brown scurf, epidermis pale green to dark brown beneath the scurf; frond scars ovate-elliptic, to 5 by 3 cm, remote, small ovate to elliptic lenticels present but inconspicuous, c. 9–15 by 5 mm, running down from each side of the petiole bases and frond scars in ± converging lines; adventitious buds absent. Fronds to 270 cm long, loosely ar- ranged around apex, in wide spiral in smaller plants, more approximate in a loose fascicle in larger plants, patent to arching, the tips drooping. Petioles to 90 cm long, inermous but densely muricate in lower half, brown to reddish brown when young due to scurf, glabrescent, dark brown to atropurpureous or blackish when older, on each side with an interrupted line of remote elongate pneumathodes, each to 20 by 2 mm, inconspicuous, brown, only present towards petiole bases; petiole scales only present in croziers, caducous in fully expanded fronds, ovate to ovate-lanceolate, to 11 by 2 mm, stramineous to dull medium brown, one apical seta, no lateral setae, margins narrow with strongly exerted cell rows, these darker brown than scale centre. Laminae to 180 by 120 cm, ovate-lanceolate, bipinnatepinnatisect to tripinnate, dark green adaxially (dark olive when dried), paler greyish green abaxially. Frond axes atropurpureous or dark brown, inermous but rhachises and costae abaxially scabrous, costae not green-alate between the pinnules in distal half. Pinnae to 60 by 20 cm, sessile, towards the lamina base also stalked to 6 cm, 11–12 pairs, often opposite or nearly so, basal ones patent to weakly reflexed, more than 1/2 the length of the longest central pinnae. Largest pinnules to 100 by 25 mm, linear-lanceolate to narrowly triangular, sessile to subsessile, the stalk to 1 mm long and hidden between the segments, base weakly cuneate, fully pinnate in lower half, basal segments free, pinnules apically attenuate; segments to 14 by 3 mm, in smaller segments the margins subentire, in larger segments coarsely crenate to inciso-serrate, veins flat to weakly raised and not contrasting adaxially, flat to weakly immersed and contrasting dark with laminar tissue abaxially, fertile veins forked. Sori proximal, to 1.0 mm diam, each with c. 40 sporangia, deeply castaneous in fresh material; indusia subsphaeropteroid to sphaeropteroid without umbo, papery, brown when dry, not translucent, receptacles globose, c. 0.2 mm diam; paraphyses absent or very few, straight, shorter than sporangia, <0.1 mm long. Spores not examined. Hairs and scales: Frond axes adaxially with pale brown to white, sometimes translucent multicellular hairs, antrorsely curved ones 1.0 mm long, with longer spreading ones, quite dense except on central and lower rhachises, abaxially without hairs, frond axes abaxially with ample fine scurf like indument on petioles, consisting of reddish brown, flat setate squamules to 0.2 mm long, also present on costules, midveins and veins but here paler and sparser; costules and midveins also with some larger ovate squamules to 0.6 by 0.3 mm, dark brown with reddish brown margins.

Distribution — Known so far only from the north-eastern escarpment of the Bismarck range in Papua New Guinea.

Habitat & Ecology — This species is found at c. 1200–2100 m in the understory of evergreen wet mountain forests, regenerating only on exposed mineral soil.

Notes — The epitype was collected under the same number as the type in the hope to encounter more fertile material soon afterwards, which would make this fragmentary collection disposable. Since this did not happen, the epitype Lehnert 2009 bis remains the only fertile material available of the species. I have chosen the sterile plant Lehnert 2009 as type because the defining scaly indument is preserved in a better condition. Morphologically, A. weidenbrueckii may be confused with A. archboldii and A. foersteri , two widespread species in New Guinea and presumably also present on adjacent islands ( Holttum 1963). These species share the presence of sphaeropteroid indusia, pale petiole scales and the lack of hairs and bullate squamules abaxially on the fronds. Alsophila weidenbrueckii is set apart from these species by the rather sharp contrast between the pale shaggy trunk and the dark shiny, glabrescent petioles; in the other species the scales are continuous from the trunk to the petioles, which are covered by longer lasting reddish scurf that obscures the comparatively pale (matte brown to yellowish) epidermis. Alsophila archboldii and A. foersteri also differ in retaining some larger elongate scales of the crozier stage in the axils of the frond axes (vs absent in A. weidenbrueckii ) and having larger scurf squamules (0.5–1.0 mm, on petioles also grading into larger scales vs uniformly <0.5 mm long on petioles and frond axes in A. weidenbrueckii ). Other species of this alliance are easily distinguished by their darker scales and scurf (most scales with darker brown central stripe in A. nigrolineata (Holttum) R.M.Tryon , almost uniformly dark brown petiole scales and dark brown squamellae covering the abaxial lamina in A. percrassa (C.Chr.) R.M.Tryon ).

In Holttums’s treatment of the family for the Flora Malesiana (1963: 79), A. weidenbrueckii may key out at couplet (54) to Cyathea insulana Holttum (= A. insulana (Holttum) R.M.Tryon ). However, A. weidenbrueckii is distinguished by having the midveins (= costules sensu Holttum 1963) not set apart so far (4 mm or less vs 5 mm or more in A. insulana ) and having paler petiole scales (pale brown vs castaneous).

Figures

Fig. 1 Alsophila weidenbrueckii Lehnert. a. Trunk apex, showing loose arrangement of fronds, blades removed, showing discrepancy between pale scurfy young petiole (upper right) and glabrescent older petiole; b. scale from petiole base; c. detail of scurf, consisting of setiferous squamellae; d. medial pinna of fertile frond; e. fertile pinnules, abaxially; f. sterile segment, abaxially; g. fertile segment, abaxially (a–d, f: based on Lehnert 2889 (BONN), e, g: based on Lehnert 2990 bis (BONN). — Scale bars: a, d = 5 cm; b, c, f, g = 1 mm; e = 1 cm. — Drawing by M. Lehnert (BONN), 2015.