Radula magna

Oliveira-Da-Silva, Fúvio R. & Gradstein, S. Robbert, 2024, High liverwort diversity in the tropical Andes as evidenced by the discovery of three new species of Radula (Radulaceae), Phytotaxa 653 (1), pp. 91-99 : 96-97

Radula magna F.R.Oliveira-da-Silva sp. nov. ( Fig. 4 )

Type:— BOLIVIA. La Paz: Inquisivi, Camillaya, western slope of Cerro Kharrata SSE of Camillaya, in Polylepis forest, on trunk, 3550–3600 m, 30 September 1997, J. Heinrichs & J. Müller JH 4039 (holotype, JE!; isotypes, MG!, MO-5131314!) .

Diagnosis:—Plants robust, 3‒5 mm wide, to 5 cm long, regularly pinnate. Stem robust, 300‒500 µm in diameter. Leaf lobes distant, oblong-ovate, margin plane to irregularly undulate, sometimes convolute ventrally. Lobules distant, reniform, base irregularly rounded, sometimes with 1‒2 short lacinia, fully overlapping and extending beyond the stem, shortly auriculate.

Description:—Dioicous? Plants 3‒4.5(‒5) mm wide, to 5 cm long, yellowish-brown in herbarium, regularly pinnate. Stems 300‒500 µm in diam., with thick-walled, brownish epidermal cells surrounding mostly larger, thin-walled, colorless to yellowish medullary cells, outer epidermal wall heavily and evenly thickened, more so than the inner epidermal wall. Leaf lobes widely spreading, distant, plane, oblong-ovate, 2.3‒2.7 mm long, 2‒2.3 mm wide, dorsal base rounded, covering up to 1/2 the stem, dorsal margin rounded, ventral margin rounded, apex rounded, margin plane to irregularly undulate, sometimes convolute ventrally, entire; marginal cells subquadrate, 10‒17 × 8‒10 µm, median cells isodiametric to elongate, 20‒30 × 17‒25 µm, basal cells isodiametric to elongate, 30‒40 × 20‒25 µm, cell walls thin, trigones lacking, intermediate thickening lacking, cuticle smooth; oil bodies 1 per cell, ellipsoidal, brownish, granular, 10–18 × 7‒13 µm. Lobules distant, reniform, 1.4‒1.6 mm long, 1.5‒1.6 mm wide, ca. 1/2 the lobe length, inflated at rhizoid area, slightly inflated along the keel, insertion 1× the base length, insertion line inverted small J-shaped, base plane, irregularly rounded, sometimes with 1‒2 short lacinia, fully overlapping and extending beyond the stem, shortly auriculate, free margin plane, irregularly rounded, apex plane, irregularly rounded to obtuse, distal margin almost straight to rounded; keel straight, spreading at angles of 40‒50º with the stem, 40‒80º with the ventral leaf margin at the junction with the lobule. Rhizoids lacking. Gametoecia and vegetative reproduction not observed.

Etymology: —The epithet “ magna ” refers to the large plants.

Distribution and habitat: — Radula magna is known from two localities in the Department of La Paz, Bolivia, viz. Cerro Kharrata (Inquisivi province) and Apolobamba natural park (Franz Tamayo province) ( Fig. 2 ). The new species was found growing on trunks of Polylepis spp. in subalpine dwarf forest at 3550‒4040 m.

Taxonomic notes: — Radula magna is characterized by the robust plants (3‒5 mm wide) with regularly pinnate branches, distant leaves and reniform lobules with a broad base, which is fully overlapping and extending beyond the stem. The leaf margins are plane to slightly irregularly undulate, and sometimes convolute ventrally. One or two short lacinia are occasionally seen on the free margin of the lobule, near the base ( Fig. 4D ). Another striking feature of the new species is the narrow angle between the lobule keel and the ventral leaf margin (40‒80º).

The material of Radula magna was originally named R. voluta . At first glance, the new species indeed resembles R. voluta due to the robust plant size and the broad lobule base. However, the lobule in R. voluta has a large voluted auricle, being circinately coiled and reaching downwards (maximally to the keel) and having a short, circinate line of insertion. Radula magna , in contrast, has a small auricle, which is not circinately coiled and has a much longer insertion line. In addition, the dorsal leaf base in R. voluta is auriculate and fully overlaps the stem, while in the new species it is not auriculate and overlaps maximally 1/2 the stem.

The new species is clearly a new member of Radula subg. Volutoradula .

Additional specimen examined:— BOLIVIA. La Paz: Franz Tamayo, Area Natural de Manejo Integrado Apolobamba, Queara, fragmento relicto del bosque de yungas altoandino, sobre Polylepis pepei B.B.Simpson , 14°43’41”S, 69°04’16”W, 4040 m, A. Fuentes et al. 12701 (paratype, MO).

Figures

FIGURE 2. Distribution of Radula ilkiuborgesiae (green dot), R. longicarinata (red triangle) and R. magna (yellow pentagon). Map made by Paulo Eduardo Silva Bezerra.

FIGURE 4. Radula magna. A. Habit. B. Marginal leaf cells. C. Median leaf cells with oil bodies. D. Leaves. E. Habit. F. Cladograph of plants. G. Cross section of stem (A, D, E = 500 µm, B, C = 25 µm, G = 100 µm; All from the holotype).