Selaginella monoloba A. R. Sm. ex C. López, Valdespino & Mostacero sp. nov.

Figs 27, 28, 29, 30, 31

Diagnosis.

Selaginella monoloba differs from S. kunzeana A. Braun by its peltate (vs. basifixed) median leaves, with two divergent (vs. parallel) auricles, axillary leaves biauriculate (vs. exauriculate), and greenish (vs. strongly hyaline) leaf margins.

Type.

Venezuela • Miranda: Parque Nacional Guatopo: near park headquarters at south entrance, 13 Feb. 1973, T. B. Croat 21688 (holotype: UC! [UC 1481428]; isotypes: MEXU!, MO! [MO -1808922], NY! [02840326], fragment PMA!, VEN! [Herb. No. 347379].

Description.

Plants terrestrial. Stems creeping to suberect, reddish, 15–45 cm long, 1.0–3.0 mm diam., articulate, not flagelliform or stoloniferous, 3–4 - branched. Rhizophores dorsal, borne on the proximal half of the stems, stout, 0.5–1.5 mm diam. Leaves heteromorphic throughout the stem and branches, chartaceous, with the upper surfaces dark green to yellowish-green and smooth, and the lower surfaces shiny yellowish-green and smooth. Lateral leaves along the main stems spreading, perpendicular to the stems, distant, narrowly oblong to oblong-lanceolate, 5.0–8.3 × 1.7–2.5 mm; bases truncate to rounded, the acroscopic bases slightly overlapping stems, the basiscopic bases with an auricle or lobe, 0.2–0.4 × 0.2–0.3 mm, free from the stems, glabrous; acroscopic margins greenish to slightly hyaline, continuously bordered by a band 1 or 2 cells wide of idioblasts, the idioblasts elongate, sinuate-walled, and papillate, the papillae in one row on each cell lumen, short-ciliate to denticulate in the basal third, otherwise dentate to denticulate distally, basiscopic margins similar to acroscopic margins, entire throughout, except short-ciliate along the distal 1 / 3; apices broadly acute to acute, tipped by 5–6 teeth; upper surfaces comprising irregularly shaped, somewhat rectangular to quadrangular, elongate, sinuate-walled cells, with stomata in 1–2 rows along the basiscopic margins and some scattered in the distal 1 / 3 of the acroscopic margins, the lower surfaces without idioblasts, comprising elongate, sinuate-walled cells, with stomata on 4–6 rows along the midribs and 6–7 rows submedial to submarginal on both halves of each leaf lamina. Median leaves peltate, non-overlapping on the main stems, imbricate on the branches, ascending, elliptic to ovate-elliptic, 2.5–3.8 × 1.2–1.7 mm; bases asymmetric and auricled, the auricles entire and divergent, the inner auricle small, broadly cuneate to rounded, 0.2–0.3 × 0.1–0.2 mm, and the outer auricle, well-developed, long rectangular, 0.6–1.0 × 0.2–0.4 mm; margins green and comprising elongate and sinuate-walled cells, the inner margin entire in the proximal 1 / 2, otherwise denticulate distally, the outer margins similar to the inner one; apices long-acuminate, each acumen 0.8–1.5 mm long, with denticulate margins, the upper surfaces puberulent with tooth-like hairs, and stomata in one row in the central portion, each acumen 0.8–1.5 mm long; upper surfaces with idioblasts and stomata in 1–3 rows along the midribs and submarginal, the idioblasts elongate and papillate, the papillae mostly in two rows on each cell lumen, but some idioblasts near the peltate base of the leaves to the stems with papillae in one row on each cell lumen and sinuate-walled, the lower surfaces without idioblasts and without stomata. Axillary leaves oblong to narrowly oblong along the main stem, 3.5–6.0 × 1.0– 1.7 mm; bases biauriculate; margins greenish, bordered by a band 1 or 2 cells wide, the cells rectangular and laevigate; margins entire along proximal half, otherwise denticulate distally; apices acute to broadly acute, tipped by 6 or 7 teeth; both surfaces similar to the lateral leaves. Strobili terminal on branch and stem tips, globose proximally, compact, and quadrangular distally, 4.0–8.0 mm long. Sporophylls ovate and of three kinds, those that subtend the microsporangia and occupy almost the whole strobilus 0.8–1.4 × 0.5–0.6 mm, and those basally located (including the megasporophyll that subtends the single basal megasporangium and the sterile sporophylls protecting it) enlarged relative to others, 1.5–1.7 × 0.6–1.4 mm; all sporophylls lacking a laminar flap, with a well-developed keel along almost the entire laminae; bases rounded; margins denticulate, greenish; apices acute tipped by 2 or 3 tooth-like projections; dorsal sporophylls (including microsporophylls and sterile sporophylls protecting the megasporangium) with the upper and lower surfaces greenish to silvery green and with irregularly elongated, sinuate-walled cells, except for the half that overlap the ventral sporophylls, where the cells are silvery-hyaline; ventral sporophylls (including microsporophylls, megasporophyll, and sterile sporophylls protecting megasporangium) with epidermal cells on both surfaces similar in shape to those of dorsal sporophylls and silvery green to hyaline. Megasporangia one per strobilus, inserted adaxially on the basal portion of the ventral sporophyll; megaspores white, the proximal and distal faces with reticulate ornamentation, the reticulae closed, each reticulum wall foveolate, with the microstructure sponge-like, 560–600 μm diam. Microsporangia many per strobilus, inserted adaxially in the two dorsal rows of microsporophylls and throughout most of the two ventral rows of microsporophylls on the strobilus; microspores tan, the proximal and distal faces with echinate ornamentation, and with laevigate to slightly rugulate microstructure, 40–50 μm diam.

Habitat and distribution.

Selaginella monoloba grows as a terrestrial, creeping plant on granitic soils along roads and rivers in the departments of Cesar and Magdalena in Colombia, and in the state of Miranda in Venezuela.

Etymology.

The name derives from the Greek “ monos, ” meaning single, and “ lobos, ” meaning lobe, referring to the single short basiscopic auricle in the lateral leaves.

Conservation assessment.

Selaginella monoloba is known from ten gatherings representing widely distributed occurrences, eight from Colombia and two from Venezuela (including the type collection). The extent of occurrence (EOO = 37 km 2) would suggest a Near Threatened (NT) conservation assessment. However, its area of occupancy (AOO = 40 km 2) indicates that this species is Endangered (EN). This is the case when one considers the environmental problems faced by the Caribbean regions of Colombia and Venezuela, including deforestation, inefficient waste disposal, air and water pollution, and soil degradation (Rodríguez 2013). The only two collections of this species from Venezuela were collected within the Guatopo National Park in the state of Miranda, a protected area; however, the collections from Colombia are many more and represent widely separated locations. The others are found in areas with a high incidence of environmental problems, such as the departments of Magdalena and Cesar (Rodríguez 2013). Accordingly, Selaginella monoloba fulfills all requirements for an assessment of Endangered [EN B 2 ab (iii)] under the IUCN Standards and Petitions Committee (2022).

Additional specimens examined (paratypes).

Colombia • Cesar: Sierra Nevada de Santa Marta, southeastern slope, Hoya del Río Donachuí, ravine SE of Donachuí, alt. 1350–1500 m, 22 Sep. 1959, J. Cuatrecasas & R. Romero C.24341 (COL, F-image, US); • Mpio. Manaure, between Cordillera Central and Santa Marta, alt. 975 m, 24 Aug. 1946, M. B. Foster & E. Smith 1585 (A); • Sierra de Perijá, Eastern of Manaure: Hacienda Nuevo Horizonte, El Podrido, alt. 1550–1600 m, 15 Nov. 1959, J. Cuatrecasas & R. Romero C.25385 (COL, US), • 16 Nov. 1959, J. Cuatrecasas & R. Romero C.25409 (COL). • Magdalena: Alto Río Frío Cabeceras del Río Congo, Ciudad Antigua, road to Alto Chimborazo, 10°59'N, 74°04'W, alt. 1100–1200 m, 26 Jul. 1989, S. Madriñan & C. E. Barbosa 510 (F-image, MEXU, MO - image, VEN); • Santa Marta, Ridge above Onaca, alt. 3000 ft [914 m], 16 Aug. 1898, H. H. Smith 2468 (F-image, GH, NCU - image, MO - image, NY - 2 sheets, MICH - image, PH - image, TEX, US - image, WIS - image, WVA - image); • Mountains above Santa Marta, alt. 3000 ft [914 m], 27 Jul. 1946, M. B. Foster et al. 1289 (COL); • Sierra Nevada de Santa Marta, Hacienda Cincinnati, alt. 1250–1500 m, 9 Aug. 1935, C. W. Martin 3209 (US - image). Venezuela • Miranda: Parque Nacional de Guatopo: trail between carretera to Summit of Morro de Aramagual, passing Río Taquasito and Río San Lorenzo, alt. 500 m, 25 Nov. 1961, J. A. Steyermark 90016 (NY, US).

Discussion.

Selaginella monoloba is characterized by its creeping to suberect habit with strongly articulated bistelic stems, leaf margins denticulate to short-ciliate, peltate median leaves with two divergent auricles: a short inner auricle overlapping the stem and a long outer auricle facing downward, lateral leaves oblong to narrowly oblong with short basiscopic auricles, and axillary leaves with two short, incurved auricles.

Initially, specimens of this species were identified as Selaginella kunzeana “ Magdalena form ” by Somers (1978) because of their resemblance to that species (e. g., basiscopic auricles on the lateral leaves, biauriculate median leaves, and similar spore size). Later, Smith (1985) cited the type collection (Croat 21688, UC) along with other specimens of this species as representing a potentially undescribed taxon, which is now formally described and validated here. Selaginella monoloba has peltate median leaves, a feature uncommon among articulated species within the genus. This character, along with short-ciliated margins bearing unicellular cilia and articulated bistelic stems, suggests that this species may belong to the Selaginella horizontalis (C. Presl) Spring complex. Members of this group share peltate median leaves, bistelic stems, and leaf margins that are serrate, denticulate, or long- to short-ciliate with unicellular cilia. Morphologically, S. monoloba is similar to S. kunzeana in its leaf shape and size, ascending to suberect habit, biauriculate median leaves, and lateral leaves with basiscopic auricles curved upward. However, it differs from S. kunzeana based on the diagnostic characters discussed.