Radula pallens var. marginata F.R.Oliveira-da-Silva, Gradst. & Ilk.-Borg.

Oliveira-Da-Silva, Fúvio Rubens, Ilkiu-Borges, Anna Luiza & Gradstein, S. Robbert, 2022, Two new Neotropical taxa of Radula Dumort. (Marchantiophyta: Radulaceae) with bordered leaves, Phytotaxa 564 (1), pp. 95-103 : 96-99

Radula pallens var. marginata F.R.Oliveira-da-Silva, Gradst. & Ilk.-Borg. , var. nov. ( Fig. 1 , 2A–C )

Radula maegdefraui K.Yamada nom. inval. (Art. 38.1, Turland et al. 2018), in Mägdefrau, Nova Hedwigia 38: 20. 1983.

Type:— VENEZUELA. Maracay: “ Nebelwald von Rancho Grande , am Weg zum Periquito ,” 1300 m, 25 February 1958, K. Mägdefrau 363 (holotype JE! , isotype MG!) .

Diagnosis:—Differs from Radula pallens (Sw.) Nees & Mont. var. pallens by the leaf lobes bordered by a row of thicker-walled cells with bulging trigones.

Description:—Dioicous. Plants 2‒3 cm long, 1.7‒2 mm wide, yellowish-green in herbarium specimens, irregularly pinnate, becoming dichotomous in upper stem portions below the gynoecia. Branches Radula - type or Lejeunea - type. Stems 170‒220 µm diameter, in cross section with ca. 30 epidermal cells surrounding ca. 55 mostly larger medullary cells, outer epidermal wall heavily and evenly thickened, more so than the inner epidermal wall, dark orange to brown, inner walls of the medullary cells thin-walled, yellowish. Leaf lobes widely spreading, imbricate, slightly convex, suborbicular, 0.9 ‒ 1.2 mm long, 0.7‒1 mm wide, dorsal base rounded, overlapping the stem, apex rounded, margin plane to reflexed, entire to usually sinuous, bordered by one row of thick-walled cells; marginal cells isodiametric, 10‒25 × 10‒20 µm, median cells isodiametric to elongate, 10‒20(‒25) × 10‒20 µm, basal cells elongate, 25‒37 × 15‒20 µm, cell walls thin, outer margin of the marginal cells strongly and evenly thickened, trigones small at leaf base becoming larger midleaf and bulging at the margin, cuticle smooth. Lobules distant, (sub)quadrate, 0.5‒0.7 mm long, (0.3‒) 0.4‒0.5 mm wide, 1/4‒1/3 the lobe length, inflated at rhizoid area, insertion line almost straight, base plane, rounded to rarely angulate, covering up to 1/2 the stem, free margin plane, straight, apex plane to incurved, rounded to slightly obtuse, distal margin plane to incurved, straight, angle with the stem 50‒60º, angle with the ventral margin of leaf lobe 160º‒170º. Rhizoids colorless to brown, scanty, present on a few lobules. Androecia not seen. Gynoecia on long branches, with 1‒2 innovations; bracts ovate, 0.8‒1 mm long, 0.5‒0.7 mm wide, apex rounded, margin plane, entire to sinuous, lobule oblong, 1/2‒1/3 of lobe length, apex rounded, keel convex. Perianth not seen. Vegetative reproduction by occasionally caducous leaf lobes.

Etymology:—The epithet of the new variety refers to the bordered leaf lobes.

Distribution and habitat:— Radula pallens var. marginata is only known from Rancho Grande in Henri Pittier National Park, northern Venezuela ( Fig. 3 ). This species was collected growing on bark in montane cloud forest, at 1300 m.

Taxonomic notes:— Radula pallens var. marginata (subg. Volutoradula) differs from the typical variety by the presence of a narrow border on the leaf lobes composed of thicker-walled margin cells with larger, bulging trigones and a thickened outer wall (border absent in var. pallens ). In addition, the leaf lobes in the new variety are sometimes caducous (caducous leaf lobes absent in var. pallens ). The leaf border seen in R. pallens var. marginata is similar to that seen in some species of the genus Odontoschisma (Gradstein & Ilkiu-Borges 2015) .

Figures

FIGURE 1. Radula pallens var. marginata. A, K. Habit with gynoecia, ventral view. B. Cross section of a leaf lobe, showing thick-walled cells at leaf margin. C. Marginal leaf cells. D, H. Cladographs of plants (U = gynoecia without perianths). E–F. Median leaf cells. G. Basal leaf cells. I. Cross section of a stem. J. Leaves in dorsal view (A, K= 1000 µm; B, I= 50 µm; C, E–G= 25 µm; H= 500 µm; A–K from the holotype). Drawing made by F. R. Oliveira-da-Silva and A. L. Ilkiu-Borges.

FIGURE 2. A–C. Radula pallens var. marginata. A. Habit, ventral view. B. Leaf lobe margin showing the border composed by thickwalled cells with large, bulging trigones. C. Cross section of stem. D–F. Radula smithii. D. Habit, ventral view. E. Leaf lobe margin showing the border composed of 3–4 rows of thick-walled, subquadrate to subrectangular or rounded cells. F. Cross section of stem (A, D= 1000µm; B–C= 50 µm; E= 200 µm; F= 100 µm; A–F from the holotype). Photograph taken by F. R. Oliveira-da-Silva.

FIGURE 3. Localization map of Radula pallens var. marginata (dot) and R. smithii (square). Map made by T. T. G. Takashima- Oliveira.