Dicksonia karsteniana, (Klotzsch) T. Moore, Ind. Fil.

Noben, Sarah, Kessler, Michael, Weigand, Anna, Tejedor, Adrian, Rodr´, Wilson D., Gallego, Luis Fernando Giraldo & Lehnert, Marcus, 2018, A Taxonomic and Biogeographic Reappraisal of the Genus Dicksonia (Dicksoniaceae) in the Neotropics, Systematic Botany (Basel, Switzerland) 43 (4), pp. 839-857 : 847-849

1. DICKSONIA KARSTENIANA (Klotzsch) T.Moore ,

Ind. Fil. 190: 313. 1860. Dicksonia karsteniana (Klotzsch) H.Karst. Fl. Columb. 2: 179. 1869, hom. superfl. Balantium karstenianum Klotzsch, Linnaea 29: 444. 1847. Dicksonia sellowiana var. karsteniana (Klotzsch) Sodiro, Recens. Crypt. Vasc. Quit. : 22. 1883.

TYPE: VENEZUELA. Aragua: Colonia Tovar, [ca. 10°24 ' 49"N, 67°17 ' 19"W, 2000–2300 m] without date, H. Karsten II 9 (lectotype B-20_0138452 !, inadvertently designated by Tryon 1989: 105, isolectotypes HBG –photo US [ 5372 , 5374 ], LE-00008012 [image], P-01414827 ) .

Dicksonia gigantea H.Karst., Fl. Columb. 2: 177. 1869.

TYPE: COLOMBIA. Cundinamarca: “Regiones nebulosas Andium Bogotensium altitudine 2600 mtr in fruticetis montis Guadalupe ”, H. Karsten s.n. (holotype not located, B?, LE?, W?; isotype P-00642549 !/- 00642550 !/- 00642551 !).

Dicksonia lobulata Christ, Bull. Herb. Boissier II , 6: 187. 1906.

TYPE: COSTA RICA. San José: Cerros de Velirla [sic], Copey de Dota [ca. 09°35 ' 12"N, 83°47 ' 57"W], 2600–2700 m, Mar 1898, A. Tonduz 11789 (holotype P-00642548 [Herb. Christ]; isotypes BM-000097864 !, BR-0000013343385 [image], K-000894776 , P-01414859 , S-R-1483 [image], US-00066375 !).

Trunks to 10 m tall, 16 cm diam including old petiole bases, adventitious root mantle blackish brown, may add significantly to diam, with skirt of old fronds, well developed in tall, exposed plants, rather scant in shaded ones. Fronds to 270 cm long, monomorphic, erect to patent, larger ones arching. Petioles mostly 5–20 cm (in juveniles to 73 cm) long, appressed to the trunk, covered with turgid, setiform, reddish to orange-brown, erect hairs to 2.5 cm long, with paler (whitish, rarely orange-brown), woolly undercoat of ciliform to catenate hairs, varying from weakly developed and evanescent to thick and persisting. Laminae to 260 X 100 cm, tripinnate-pinnatifid, coriaceous, obovate to oblanceolate. Frond axes (rachises, costae, and costules) with varied indument, adaxially with persistent antrorsely curved to spreading hairs, relatively sparse on lower part of rachis, always dense on costae and costules, abaxially first with soft matted woolly hairs (undercoat), often worn off in older fronds, leaving costae and costules with pale or reddish ciliform hairs, spreading, sparse. Pinnae to 53.5 X 16.0 cm, sessile, oblong-lanceolate with attenuate tips, 15–20 pairs per frond, lower pairs reduced to ca. 1/4–1/10 length of longest medial pinnae, lowest ones pinnatifid with thin costae, appearing like a pinnule of medial pinnae. Pinnules to 9.0 X 1.8 cm, oblong- to triangular-lanceolate, basally auriculate, sessile to very short stalked. Segments 9.0 X 3.5 mm, sessile, oblique, weakly falcate, lobed to slightly dissected, margins flat to weakly revolute, proximal segments larger than medial ones. Midveins slightly to moderately hairy, hairs whitish, to 1.5 mm long, lateral veins glabrous. Sori 1.5–2.0 mm in diam, oblong when closed, circular when open, on the acroscopic and basiscopic side of the segment, one sorus per lobe, at the end of simple lateral veins, distance receptacle–midvein 0.7–1.5 mm. Indusia bivalved, outer one brown with entire cartilaginous margin, inner one light brown with subentire to slightly erose margins, beset with hyaline obovate cells; paraphyses catenate, contorted, longer than sporangia. Spores tetrahedral-globose with prolonged, depressed lobes, ca. 57 X 38 μm, exospore smooth, perispore bacillar-granular. Figures 1B, F, G, H , 5A–C .

Etymology —Named after G. C. W. Hermann Karsten (1817–1908), the German botanist who collected the type specimen and compared the three taxa formerly included in Dicksonia sellowiana in his Flora Columbiae.

Distribution and Habitat —Rare in Costa Rica, common in the Andes from Colombia to Venezuela and Bolivia, in cool mountain rainforest to sub-páramo and open grassland at (1200–)1800–3300(–3600) m ( Fig. 6 ).

Notes —After careful comparison, we subsume the name D. gigantea under D. karsteniana , based on laminar characters and further corroborated by the following observations. The type locality near Bogotá at 2600 m falls into the general range and preferred elevation of D. karsteniana , and all complete specimens that we have seen from the mountains around the Bogotá valley are clearly assignable to D. karsteniana . As delimited here, the taxon formerly known as “ D. gigantea ” ( Lellinger 1989) , here recognized as D. navarrensis , occurs mainly west of the Cordillera Occidental of Colombia below 2000 m, whereas D. karsteniana is commonly found in the main range of the Andes above 2000 m. Dicksonia navarrensis is prevalent in Mesoamerica but there is a geographical overlap in Costa Rica, where D. karsteniana also occurs at higher elevations.

Dicksonia karsteniana is a wide-ranging species in distribution and elevation. We observed two extremes in the hairy indument of D. karsteniana that can be related to external factors: One with the outer layer of straight reddish brown hairs weakly developed on the petioles in favor of a denser, longer lasting woolly pale undercoat that extends all along the rachis, and the other one just the opposite, with well developed and exceptionally dark straight hairs but almost no undercoat and glabrescent distal petioles and rachises. In comparison with the other taxa that we here recognize, these differences may seem equally valid for treating the extreme forms of D. karsteniana as separate species. However, we were able to observe several larger populations where most plants are intermediate in indument characters (i.e. outer layer and undercoat both well developed, the latter first covering upper petiole and rachis but soon caducous) and that extreme forms are correspondingly found in extreme habitats. For instance, persistent white woolly hairs on petioles and rachises are found in plants from exposed and cold conditions at high elevations. These plants are also smaller than average, rarely surpass 2 m trunk height and have fronds just ca. 125 cm long. Additionally, we observed transitions between the hairy and the regular form, e.g. in Ecuador along the mountain pass of Gualaceo towards the village of San Carlos de Limón, and in Colombia around the Laguna de la Cocha, where open páramos and closed elfin forests change quickly. More glabrescent plants with darker, straight petiole hairs are usually found at low population densities below 2000 m, growing in sheltered gullies and deep ravines that are notably cooler than the surrounding terrain. These individuals often attain the maximum length of fronds as given in the description but differ from plants from higher elevations in having the distal pinnae and outer pinnules/segments more ascending and more asymmetric (basiscopic side more pronounced). Furthermore, the low elevation plants constantly have soral diameters that are near the minimum of D. karsteniana (1.5 mm) and thus are at first glance more similar to D. navarrensis in this regard. The hairy form of Dicksonia karsteniana had been previously segregated as D. sellowiana var. arachneosa Sodiro , named for the hairs that are preserved in a cobwebby manner on the rachises and costae of dried specimens. The glabrescent extreme formed the basis for the synonym Dicksonia spruceana Mett. ex Kuhn. Simply to be able to discuss these forms more easily in floristic treatments, we give them names at varietal status based on the available epithets, and provide a key. At the same time, we want to point out that many specimens may not be unambiguously assigned to a variety. The species is more common in Ecuador than documented here (see Fig. 6 ) but we had no opportunity yet to reassess the plethora of specimens in the local herbaria.

VARIETIES Of DICKSONIA KARSTENIANA

1. Darker petiole hairs tangled and relatively few, transient with a denser, paler woolly undercoat; hairs adaxially on frond axes mostly pale (pale brown to grayish white, rarely mixed with partially red hairs) and spreading; hairs abaxially on rachises and costae spreading to matted, mostly whitish, rarely orange-brown, 2–5(–10) mm long, persisting in mature fronds (absent or fewer shorter hairs on costules and veins), leaving a strongly scabrous surface when abraded. [High elevations from Venezuela to N Peru]............................... D. karsteniana var. arachneosa

1. Darker petiole hairs spreading at petiole base, differentiated from shorter woolly undercoat; hairs adaxially on frond axes mostly dark red-brown to blackish and appressed; hairs on frond axes abaxially if present soft and matted, evanescent, largely missing in mature fronds, costules and costae distally with few spreading hairs <2 mm, leaving a smooth to faintly scabrous surface when abraded............................................ 2

2. Petioles with a discernable white undercoat persisting under outer layer of dark straight hairs, hairs on rachises and costae abaxially leaving a faintly scabrous surface; at least some sori kidney-shaped when closed and to 2 mm wide. [Range of the species]................................ D. karsteniana var. karsteniana

2. Petioles without discernable white undercoat, faintly developed or evanescent, only outer layer of dark straight hairs persisting; hairs on rachises and costae abaxially leaving a smooth surface; all sori ± round when closed and 1.5 mm wide. [Lower elevations of eastern Andean slopes]................................................... D. karsteniana var. spruceana

Figures

FIG. 1. Important characters of Andean Dicksonia in the field. A–C. Trunk and leaf arrangement of plants growing outside the forest. A. Dicksonia lehnertiana, short trunks ca. 0.8 m tall, no skirt of old fronds (Anori, Dept. Antioquia, Colombia). B. Dicksonia karsteniana var. arachneosa, trunks ca. 1.7 m tall, with skirt of old fronds (La Cocha, Dept. Nar~ no, Colombia). C. Dicksonia stuebelii, trunks 2–3.6 m tall, fronds characteristically erect, dead fronds persisting but not forming skirt (Colan, Dept.Amazonas, Peru).D–I. Hairs on petioles.D.Spreading bristly hairs, D.lehnertiana (Yarumal, Dept.Antioquia, Colombia). E. Matted hairs, paler undercoat exposed by emerging adventitious buds, D. navarrensis (Dept. Caldas, Colombia). F. Thick white undercoat with longer darker hairs emerging, D. karsteniana var. arachneosa (La Cocha, Dept. Nari~ no, Colombia). G. Woolly hairs, left D. karsteniana var. arachneosa (or probable hybrid) with D. stuebelii, right (Molinopampa, Prov. Amazonas, Peru). H. Spreading soft hairs, undercoat weakly developed to absent, D. karsteniana var. spruceana. I–J. Adventitious buds I. Buds with small coiled-up croziers (dashed circles), at base of rotting petiole still attached to trunk (right), D. navarrensis (Colombia). J. Small plant from such a bud growing in root mantle of mother plant, D. navarrensis (Panama). All pictures © M. Lehnert except for C, © A. Tejedor.

FIG. 5. Important characters of Neotropical Dicksonia. A. Dicksonia karsteniana var. karsteniana. (A1 from Lehnert 1000, GOET; A2, A4 from Mostacero and Castillo 275, UC, from locus classicus of the species; A3 from Delascio-Ch. 9063, UC). B. Dicksonia karsteniana var. arachneosa. (B1, B4 from Lehnert 2323, STU; B2 from Cumbicus et al. 457, STU). C. Dicksonia karsteniana var. spruceana. (C1, C2 from lectotype, Spruce 4728, K; C3, C4 from Quipuscoa et al. 2630, UC). D. Dicksonia navarrensis.(D1–D4 from Lehnert 3493 with Tejedor, BONN). A1–D1. Petioles, showing lower parts, either with spreading hairs (A1–C1) and varying undercoat (well developed in B1), or all hairs matted (D1). Lowest pinnae tapering, often reaching down to petiole base (A1), may be substituted for adventitious buds (D1). A2–D2. Pinnules, adaxially (not shown for B).Large ones (A2, D2) showing typical form with slightly asymmetric base, which may be more notable in smaller pinnules from pinna apex (C2). A3–D3. Sterile segments, abaxially. A4–D4. Fertile segments, abaxially.

FIG.6. Distribution of Dicksonia in South America. A. Dicksonia karsteniana (squares), D.sellowiana (dots). Inset: varieties of D. karsteniana, var. arachenosa (triangles), var. spruceana (asterisks). B. Dicksonia lehnertiana (crossed circle), D. navarrensis (triangles), D. stuebelii (stars; occurrence in northern Colombia).