Dicksonia lehnertiana Noben, F.Giraldo, W.Rodriguez and A.Tejedor, 2018

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 : 851

2. Dicksonia lehnertiana Noben, F.Giraldo, W.Rodriguez and A.Tejedor , sp. nov.

TYPE: COLOMBIA. Antioquia: Yarumal, Sector Morro Azul , antiguo camino a Cede ~ no, 06°57 ' 24"N, 75°33 ' 51"W, 2550 m, 13 Mar 2000, F. Giraldo and S. Mej´ ıa 1964 (holotype HUA!; isotype JAUM!).

Compared to other Neotropical species of the genus, Dicksonia lehnertiana is relatively small and stands out by having persistent, dark reddish brown, spreading bristly hairs on petioles and leaf axes paired with a very thin pale undercoat. The other species have the hairs not bristly ( D. sellowiana , D. karsteniana var. spruceana ) and usually also a thicker undercoat ( D. karsteniana var. karsteniana ) that may be dominant in the petiolar indument ( D. karsteniana var. arachneosa , D. navarrensis , D. stuebelii ).

Trunks to 1.5 m tall, 10–12(–25) cm in diam, including cover of persisting petiole bases, dead fronds may be retained for some time but not accumulating in a persistent skirt, usually without; adventitious root mantle weakly developed; adventitious buds absent. Fronds to 200 cm long, monomorphic, erect to patent, larger ones arching. Petioles relatively long, (20–) 45–90 cm, 1/4–1/2 of frond length, appressed to the trunk for 10–20 cm, densely covered for all of its length with spreading, long, stiff hairs to 2.5 cm long, dark reddish brown, their bases indurated, persisting, the tips flexuous to soft, inconspicuous undercoat of pale (white to light brown) lightly matted catenate hairs with short ciliform tips, dense, persisting. Laminae 110–150 X 50–75 cm, bipinnate-pinnatifid to tripinnate, coriaceous, elliptic or obovate. Frond axes (rachises, costae and costules) with a similar hairy indument as the petiole, ± antrorsely curved, becoming gradually shorter (ca. 2 mm long), spreading hairs and undercoat approximating each other regarding color and structure toward costules; hairs adaxially less spreading than abaxially, hairs persisting to long lasting, leaving a scabrous surface if removed. Largest pinnae 25–38 X 14 cm, pinnae sessile, triangular- to oblong-lanceolate with attenuate tips, 12–16(–18) pairs per frond, the basal ones mostly 1/2 the length of longest pinnae, rarely 3–4 basal pairs tapering to almost pinnule size (but then pinnae still with thick costae, and free petiole part substantial). Pinnules to 7.5 X 1.8 cm, sessile, basally auriculate, oblong-triangular to lanceolate. Segments to 7.0 X 3.3 mm, sessile, basally patent, distally weakly oblique, straight to weakly falcate, margins crenate to serrate, flat to weakly revolute; proximal segments either the largest or not significantly smaller than following ones. Veins adaxially glabrous except for a few scattered ciliform hairs to 1 mm long on midveins, abaxially densely hairy on the veins, few to many between the veins, hairs to ciliform to partly catenate, pale (whitish to yellowish brown) to partially red, especially on midveins. Sori (1.2–) 1.4–1.8 mm in diam, oblong when closed, circular when open, on the acroscopic and basiscopic side of the segment, one sorus per unbranched lateral vein, distance receptacle to the midvein 0.8–1.0 mm; indusia bivalved, outer one brown with entire cartilaginous margin, inner one dark brown with erose to weakly lacerate margins bearing small hyaline obovate cells; paraphyses dark red, catenate with clavate tip, tortuous, slightly longer than sporangia. Spores tetrahedral-globose with prolonged, depressed lobes, spores not measured, exospore smooth, perispore bacillar-granular. Figures 1A, D , 7A .

Etymology —The main author and co-authors of this paper take great pleasure in naming this species after Dr. Marcus Lehnert (1975–), senior author of this paper, in recognition to his outstanding contribution to fern research in general, and our knowledge of tree ferns in particular.

Distribution and Habitat —Northern Colombia at 2500– 2650 m in low montane forest with strong Caribbean influence. May occur in adjacent N Venezuela where similar conditions are found ( Fig. 6 ).

Additional Specimens Examined (Paratypes) — Colombia. — ANTIOQUIA: Yarumal, Morro Azul , 06°59.261’N, 75°24.413’W, 2550 m, 01 Feb 2015, M. Lehnert 3017, 3019, 3020 with M. Kessler, W. Rodriguez, F. Giraldo ( BONN, HUA) ; Morro Azul, o Cerro La Marconi , Camino viejo a Cede ~ no, 6.9567861 N, 75.5643861 W, 2650 m, 12 Aug 2001, F. Giraldo 2573 ( HUA, JAUM) .

Discussion —The species was already recognized as distinct by F. Giraldo in 2000, but its description was postponed until a thorough taxonomic reappraisal of the Neotropical species of the genus was available. Dicksonia lehnertiana is a peculiar species in that it shows features of juvenile plants of other Neotropical Dicksonia species, like overall small size, ± ovate laminae, and long petioles with stiffly spreading hairs and weakly developed undercoat. At its presently known occurrences, however, it grows in large quantities without any other Dicksonia species growing nearby. Its preference for open habitats may argue for an ecological adaptation of a more widespread species like D. karsteniana , but this can be dismissed for two reasons. First, D. lehnertiana keeps its distinguishing characters (e.g. stiffness of hairs) when it ventures into the forest understory. Second, other Dicksonia taxa show the tendency to increase the woolly undercoat and shorten the petioles when growing under exposed conditions, as observed in D. karsteniana var. arachneosa and D. stuebelii .

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. 7. Important characters of Neotropical Dicksonia. A. Dicksonia lehnertiana. A1. Petiole. A2. Fertile pinnule, abaxially. (Lehnert 3019, BONN). B. Dicksonia stuebelii. B1. Petiole.B2. Fertile pinnule, abaxially (Sanchez 11111, UC). C.Dicksonia sellowiana. C1. Petiole, hairs only persisting near base (Hatschbach 43455, US). C2. Sterile pinnule, adaxially. C3. Immature fertile segments abaxially, with costae still covered in woolly undercoat. C4. Fertile segments abaxially, sori fully developed. D. Dicksonia antarctica. D1. Crozier, showing easily abraded woolly undercoat. D2. Fertile segments abaxially, with glabrescent costae and costules. (C2–C4, D: from living plant at Botanic Garden Bonn).

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).