Micropterygium longicellulatum Uribe & E. Linares, 2015

Uribe-M, Jaime & Linares, Edgar L., 2015, Micropterygium longicellulatum (Lepidoziaceae, Marchantiophyta), a new species from Colombia, Phytotaxa 213 (3), pp. 296-299 : 298-299

Micropterygium longicellulatum Uribe & E. Linares , sp. nov., Fig. 1

The new species differs from all known species of genus Micropterygium by its very long leaf cells, with a length-width ratio 4–9:1, with repand margins and thickened walls.

Type:— COLOMBIA. Chocó, vereda Rionegro, Cerro del Torrá, vertiente oriental, ca. 1920–1950 m, 8 Ago 1988, Philip A. Silverstone-Sopkin, et al. 4213 (holotype COL 472563 !; isotype, CUVC!) .

Plants epiphytic, in dense tufts, ascending or erect from branched rhizome, pale green to yellowish, main shoot with leaves 3–4 mm wide and up to 10 cm long. Stems of main shoot, in cross section elliptical, 300–350 × 200–220 μm wide; with one row of epidermal cells, reddish, with thick walls, 30–37 × 50–57 μm, and ca. 40 medullary cells, 25 × 55 μm, with very thin walls; branching irregularly pinnate, branches intercalary (lateral and ventral), lateral branches leafy, arched, Radula - type, 2–3 mm long; ventral-intercalary microphyllous branches, flagelliform, 1.5–2 mm long. Stem leaves patent, imbricate, succubous, symmetrical, deeply concave to concave-conduplicate, insertion line transverse, ovate-lanceolate, 1.5–1.8 mm long, 0.4–0.5 mm wide in lateral view, margin serrate to ¾ of its length, teeth cells 40–47 × 9–11 μm, keeled, wing apparent on the upper half of lamina, to 4 cells in the widest portion, apex long spinose, 2 cells wide, 0.36–0.38 mm long, leaf cells rectangular, repand, fusiform; median cells with thin walls, 43–77 × 8–11 μm; basal cells with thickened walls, reddish, 34–41 × 8–16 μm; trigones inconspicuous or absent; cuticle smooth. Underleaves ovate to oblong-ovate, apex truncate and coarsely dentate, concave, entire, margins dentate from the middle to the apex, 1000–1150 × 700–950 μm, to 2 times wider than the stem, they are not reduced in size towards the plant apex, median cells 60–90 × 8–16 μm, apex dentate, cell 30–34 × 13–17 μm. Perianth: 8–12 mm long; protected by 3-series of bracts and bracteoles; lanceolate to oblong-lanceolate, the mouth contracted, long-ciliate.

Ecology and distribution: — Micropterygium longicellulatum is known from several collections from Cerro del Torrá, Chocó, Colombia, occurring on living trees and logs, in very humid sites, in mountain wet cloud forests, at ca. 1900–2400 m elevation.

Etymology: —The name of this species refers to the leaves cells, which are very long, to 80 μm, with length to width ratio 9:1.

Paratypes:— COLOMBIA. Chocó. San José del Palmar, vereda Rionegro, Cerro del Torrá , vertiente oriental, vegetación secundaria mezclada con bosque nublado primario al lado de trocha arriba de helipuerto, 1920–1950 m, 8 Ago. 1988, Philip A. Silverstone-Sopkin, N. Paz, R. T. González, J. E. Ramos, C. H. Ramos & A. Henao 4197 ( COL 472665 ) 4198 ( COL 472483 ), 4200 ( COL 472629 ), 4201 ( COL 472630 ), 4215 ( COL 472625 ) ; 1900 m, 15 Ago. 1988, J. E. Ramos & P. A. Silverstone 1238 ( COL 472686 ) ; trocha entre helipuerto y mesa (debajo de cumbre), bosque nublado primario, 1940–2450 m, 30 Ago. 1988, Philip A. Silverstone-Sopkin, N. Paz, R. T. González, J. E. Ramos, C. H. Ramos & A. Henao 4920 ( COL 472673 ), 4920 A ( COL 472672 ) .

Key to Colombian species of Micropterygium (adapted from Fulford, 1966 and Schuster, 2000)

1. Leaves cells very long, to 80 μm, with length: width ratio of 9:1; leafy shoots with radial symmetry ................ M. longicellulatum

– Leaves cells isodiametric, quadrate or subquadrate, with length-width ratio of 1–1.5:1 Leafy shoots with dorsiventral symmetry .. ............................................................................................................................................................................................................2

2. Leaf cells with cuticle smooth, more or less plane.............................................................................................................................3

– Leaf cells with a single large mamillose projection, strongly convex................................................................................................7

3. Underleaves in form and size, very similar to leaves, not decreasing in size toward the apex..........................................................4

– Underleaves gradually smaller along the stem...................................................................................................................................6

4. Leaves keeled above apex, not conspicuously folded ................................................................................................. M. leiophyllum

– Leaves keeled throughout their length, completely folded ................................................................................................................5

5. Leaf apices rounded, wing very broad ............................................................................................................................... M. lechleri

– Leaf apices acute, wing narrow ................................................................................................................................ M. reimersianum

6. Leaf and wing margin entire........................................................................................................................................... M. carinatum

– Leaf and wing margin serrate, dentate or incised.................................................................................................. M. pterygophyllum

7. Underleaves not decreasing in size toward the apex of stem ................................................................................... M trachyphyllum

– Underleaves becoming smaller toward the tip of the stem....................................................................................... M. parvistipulum

Comments: —According to Schuster (2000) species of subg. Micropterygium are characterized by bilateral symmetry and an anisophyllous leafy stem and species of the subg. Pseudolembidium are isophyllous or subisophyllous and have radial symmetry. By symmetry, M. longicellulatum would belong to subg. Pseudolembidium, but would belong to subg. Micropterygium by the strongly anisophyllous leafy stems. The existence of a new species of the genus that combines the two characteristics used by Schuster to separate the subgenera proposed by him, reaffirms the urgent need for taxonomic revision of Micropterygium , with molecular methods.

Micropterigyum longicellulatum seems to be most closely morphologically allied to the Venezuelan M.steyermarkii Fulford (1966: 270) and M. grandistipulum Stephani (1901: 98) from Venezuela and British Guiana by its radial symmetry. However, in M. grandistipulum the wing extends from the apex to below the middle of the leaf, whereas in M. steyermarkii the wing extends the entire length of leaf. Both species have entire margins and the leaf cells are round-quadrate, in addition, M. steyermarkii , has a coarsely mamillose leaf surface ( Fulford 1966).

All species recorded so far in Colombia have a dorsi-ventral symmetry. However, M. longicellulatum seems closely allied to M. trachyphyllum and M. parvistipulum since they share dorsal and ventral lobes that are more or less equal, but the later two species have their wings extending to the leaf base ( Fulford 1966), and the leaf cells are round-quadrate.

Figures

FIGURE 1. Micropterygium longicellulatum. A. Part of shoot, ventral view. B. Stem leaf. C. Stem in cross section. D. Median leaf cells. E. Wing cells. F. Basal leaf cells. G. Apical leaf cells. (All drawn from the type, Silverstone-Sopkin, et al. 4213).