Selaginella papillosa Valdespino, 2020

Valdespino, Ivan A., 2020, Taxonomic innovations in South American Selaginella (Selaginellaceae, Lycopodiophyta): description of five new species and an additional range extension, PhytoKeys 159, pp. 71-113 : 71

Selaginella papillosa Valdespino sp. nov. Figures 6 , 7 , 8 , 9

Diagnosis.

Selaginella papillosa differs from S. brevifolia by its median leaf inner and outer halves equal in width (vs. outer halves typically wider than the inner halves), lateral leaf upper surfaces with midribs not marked and of the same color as the rest of the laminae (vs. well-marked and straw-colored), acroscopic margins long-ciliate along proximal ¼ -⅓ or occasionally proximal ½ (vs. ½-¾), and axillary leaf ovate or ovate-lanceolate (vs. ovate-deltate).

Type.

Venezuela. Amazonas: Río Negro, Río Siapa near base of Cerro Aracamuni, 01°39'N, 65°40'W, 250 m, 4 Nov 1987, R.L. Liesner & G. Carnevali 22750 (holotype: NY!; isotypes: MO!, NY!, UC!).

Description.

Plants epipetric, moss-like. Stems creeping, stramineous, 5.0-15.0 cm long, 0.3-0.5 mm diam., non-articulate, not flagelliform, not stoloniferous, straw-colored, 1 or 2-branched, the branches arising at almost 90° angle. Rhizophores axillary, axillary-ventral or dorsal, borne throughout the stems, filiform, 0.1-0.2 mm diam. Leaves heteromorphic throughout, membranaceous, upper surfaces light green, lower surfaces silvery green. Lateral leaves distant, spreading to slightly ascending or slightly imbricate (at branch tips), ovate, 1.0-2.0 × 0.8-1.6 mm; bases rounded, glabrous, acroscopic bases overlapping stems, basiscopic bases free from stems; margins on upper surfaces greenish and composed of quadrangular to rounded cells, on lower surfaces bordered continuously by a hyaline band comprised of idioblasts, the band 1-3 cells wide, the idioblasts elongate, straight-walled, and papillate, the papillae in a single row over each cell lumen, acroscopic margins long-ciliate along proximal ½ -⅔, otherwise dentate distally, basiscopic margins dentate along proximal ⅔, otherwise denticulate distally; apices acute, attenuate to apiculate, apiculae often falling off, tipped by 1 or 2 teeth; upper surfaces mostly glabrous, except for few, distal, teeth-like hairs near apices, comprising rounded to quadrangular, sinuate-walled, papillate cells, each cell lumen with 7-14 papillae, with few (ca. 4) submarginal to marginal stomata near central portion of basiscopic margins, lower surfaces glabrous, comprising elongate, sinuate-walled, laevigate cells and of straight-walled, papillate idioblasts, the papillae 9-15 in one row on each cell lumen, with stomata on 1-3 rows along midribs. Median leaves distant to slightly imbricate near branch tips, ascending, ovate to broadly ovate to ovate-orbiculate or elliptic with both inner and outer halves equal in width, 0.8-1.2 × 0.5-1.0 mm; bases glabrous, oblique and decurrent, without auricles; inner margins bordered continuously by a narrow hyaline band comprised of idioblasts, the band 1 or 2 cells wide, the idioblasts similar to those in the hyaline marginal bands of the lateral leaves on lower surfaces, except for papillae sometimes interconnecting, long-ciliate along proximal ¾, otherwise short-ciliate to dentate distally, the outer margins bordered by greenish, quadrangular to elongate, glabrous cells along proximal ½ and along distal ½ by a hyaline band comprised of idioblasts, the band 1-5 cells wide, the idioblast similar to those in the inner margins, dentate throughout; apices aristate, each arista 0.2-0.4 mm long, tipped by 1 or 2 teeth; upper surfaces glabrous, comprising rounded, sinuate-walled, papillate cells, each cell lumen with 4-15 papillae, concentrically arranged, without idioblasts, with stomata in 1 or 2 rows along midribs on distal ½ of the leaf lamina and few (1 or 2) marginal to submarginal along proximal ½ of outer margins, lower surfaces comprising elongate, sinuate-walled, glabrous cells and submedial to submarginal, sinuate-walled, papillate, idioblasts cells, the papillae similar to those in lower surfaces of lateral leaves, without stomata. Axillary leaves ovate to ovate-lanceolate, 1.2-1.5 × 0.6-1.0 mm; bases attenuate and covered by idioblasts similar to those in lower surfaces of lateral leaves, except for papillae in 1 or 2 rows on cell lumen; margins on upper and lower surfaces as in lateral leaves, ciliate along proximal ½-¾; apices acute, attenuate to apiculate, apiculae often falling off; both surfaces as in lateral leaves. Strobili terminal on branch tips, quadrangular, 0.4-5 mm long. Sporophylls monomorphic, without a laminar flap, each with a slightly developed keel along midribs, the keel glabrous or with few, short, tooth-like projections distally, ovate-lanceolate, 0.6-1.0 × 0.3-0.5 mm; bases rounded; margins narrowly bordered by a hyaline band, the band 1 or 2 cells wide with the cells elongate, slightly sinuate-walled and glabrous, shortly ciliate along proximal ½, denticulate on distal ½ or denticulate throughout; apices attenuate to acuminate, the acumen 0.1-0.3 mm long, tipped by 1 or 2 teeth; dorsal sporophylls with upper surfaces green and cells as in median leaves, except for the half that overlaps the ventral sporophylls where the surfaces are greenish hyaline to hyaline with elongate and slightly sinuate-walled cells, lower surfaces hyaline and comprising elongate, sinuate-walled cells; ventral sporophylls with both surfaces, hyaline, comprised of elongate, papillate, sinuate-walled cells. Megasporangia few and proximal, along two ventral rows; megaspores yellow, pale yellow to whitish, 270-310 µm diam., proximal faces rugulate-reticulate with a well-developed equatorial flange, the microstructure echinate and perforate, distal faces reticulate, the reticulae open (incomplete) to closed, the microstructure echinate and perforate. Microsporangia in two dorsal rows and distally along two ventral rows; microspores light orange, not measured or observed in detail.

Habitat and distribution.

Selaginella papillosa grows at 250-1670 m in tropical rainforests at the base of Cerro Aracamuni and near the summit of Cerro Aratitiyope in the state of Amazonas, Venezuela.

Etymology.

The specific epithet derives from the Latin " papilla," meaning “nipple”, and refers to the abundant and distinctive papillae found on cells lumen in upper, leaf surfaces.

Conservation status.

Selaginella papillosa is only known from two collections made at the base of Cerro Aracamuni, a Guiana Highland sandstone tepui, part of the Serranía de La Neblina National Park, and near the top of Cerro Aratitiyope, a granitic mountain designated as a Natural Monument, both in the state of Amazonas, Venezuela. Accordingly, the natural populations of this new species may not be threatened. However, as available data is scanty, it does not allow for a reliable conservation assessment. Therefore, the species is considered Data Deficient (DD) based on IUCN (2012).

Additional specimens examined (paratypes).

Venezuela. Amazonas: Río Negro, Cerro Aratitiyope, ca. 70 km al SSW de Ocamo, 02°10'N, 65°34'W, 990-1670 m, 24-28 Feb 1984, Steyermark et al. 130146 (MO-2 sheets, UC pp [mixed with some scraps of S. tuberculata Spruce ex Baker]).

Discussion.

Selaginella papillosa is distinctive by its moss-like habit, lateral leaf with long-ciliate acroscopic margins along proximal ½ -⅔ and acute, attenuate to apiculate apices, with apiculae often falling off and tipped by 1 or 2 teeth, the upper surfaces glabrous, except for few, distal, teeth-like hairs near apices, and with few submarginal to marginal stomata near central portion of basiscopic margins. In addition, its leaf upper surfaces are comprised by rounded to quadrangular, sinuate-walled, papillate cells, each cell lumen with many (i.e., 7-14) papillae, and with margins bordered by elongate, straight-walled, papillate idioblasts on lower leaf surfaces. Finally, its median leaf upper surfaces have marginal to submarginal stomata along proximal ½ of outer margins.

Selaginella papillosa is a member of the " Selaginella deltoides group" as defined by Valdespino (2016). Among species in that alliance it is morphologically close (e.g. in habit, leaf, and overall megaspore sculpturing pattern) to S. aculeatifolia and the here described S. pubimarginata (see for discussion). These three species might, in addition, be sympatric, as they have been collected in the Guiana Highland region of Venezuela at similar low to mid elevations. Selaginella papillosa differs from S. aculeatifolia by its lateral leaf upper surfaces with few (vs. without) submarginal stomata along central, basiscopic portion of the laminae, with 3-5 (vs. many, ca. 50) short hairs or tooth-like projections near distal most portion of apices (vs. along distal ½ of basiscopic halves and apices), with midribs inconspicuous (vs. conspicuous, outlined by elongate, straight-walled and papillate idioblasts), and acute to apiculate (vs. long-acuminate) apices. It is further differentiated from the latter by its median leaves broadly ovate to ovate-orbiculate or elliptic (vs. broadly ovate to ovate-elliptic), with oblique and decurrent (vs. oblique or rounded) bases, and stomata present on upper leaf surfaces along distal ½ (vs. ¾) and with few (vs. without) stomata submarginally to marginally along proximal ½ portion of outer margins. Furthermore, its megaspores proximal and distal faces microstructure consists of long- (vs. short-) echinae.

Selaginella papillosa was confused in the past with S. brevifolia and, in fact, its type collection was originally identified as the latter species. Selaginella papillosa differs from S. brevifolia by the characters listed in the diagnosis and by its lateral leaf having only very few, i.e., 4-6 tooth-like short hairs near the apices, whereas the latter species has many of these hairs along the basiscopic halves of the laminae and toward the apices.

Selaginella papillosa is also set aside from the similar S. albolineata by its median and lateral leaves upper surfaces without (with many, elongate) idioblasts and acroscopic margins long-ciliate along proximal ½ -⅔, otherwise denticulate distally (vs. entire to scarcely denticulate throughout), and median leaf inner margins long-ciliate (vs. denticulate).

The paratype specimen of S. papillosa (Steyermark et al. 130146 at MO) was originally identified as S. revoluta Baker, vel aff., a species that is the center of a species group described by Mickel et al. (2004). Selaginella papillosa is a rather more slender species than S. revoluta and differs further from the latter by its median leaves ovate to broadly ovate to ovate-orbiculate or elliptic (vs. broadly ovate, ovate orbicular to ovate-rhombic) with oblique to decurrent (vs. subcordate) bases, and apices with rather narrow and needle-like (vs. broad and subulate) long aristae, each without (vs. with tooth-like) hairs on its surfaces. Finally, S. papillosa could also be compared to S. hirtifolia Valdespino, which is not morphologically close to it but rather is a member of the S. revoluta group. Selaginella papillosa is easily separated from the latter by its lateral leaf upper surfaces almost completely glabrous (vs. with short, teeth-like hairs along the basiscopic, submarginal region and near apices) and long-aristate (vs. acuminate) median leaf apices with the arista hyaline (vs. with the acumen green).

Figures

Figure 6. Selaginella papillosa Valdespino. A Section of upper surface of stem showing median and lateral leaves B median leaf, upper surface C distal half of median leaf, upper surface (same leaf shown in B) D proximal half of median leaf, upper surface (same leaf shown in B) E section median leaf inner half, upper surface; note prominent papillae on cells (E 1) F detail of midsection of median leaf, upper surface G lateral leaf and sections of median leaves, upper surface H portion of basiscopic margin of lateral leaf, upper surface; note submarginal stomata (a) I distal half of lateral leaf, upper surface, note short hair on leaf surface (a). A-I taken from the holotype.

Figure 7. Selaginella papillosa Valdespino. A Section of lower surface of stem showing lateral leaves and axillar leaf B lateral leaf, lower surface C proximal half of lateral leaf, upper surface (same leaf shown in B) D distal half of lateral leaf, upper surface (same leaf shown in B) E detail of lateral leaf, lower surface; note elongate, papillate idioblasts with papillae interconnected (a) F detail of outer half of median leaf, lower surface; note elongate, papillate idioblasts (a) G axillary leaf and portion of lateral leaves, lower surface H portion of proximal half of axillary leaf, lower surface (same leaf shown in G) I distal half of axillary leaf, lower surface (same leaf shown in G). A-I taken from the holotype.

Figure 8. Selaginella papillosa Valdespino. A Megaspore, proximal face B detail of megaspore, proximal face C megaspore, distal face D detail of megaspore, distal face. A-D taken from the holotype.

Figure 9. Distribution of Selaginella papillosa *, S. pubimarginata ◊, S. rostrata ■.